Hi and welcome to the forum
Can you return any of that stuff you ordered?
API Stress Coat dechlorinates the water and helps reduce damage to the fish from poor water quality (ammonia, nitrite, etc). If you have a basic water conditioner/ dechlorinator, then you don't need both. You can use one or the other to dechlorinate the water.
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API Stress Zyme is not necessary. It helps to break down rotting organic matter in the gravel and that gunk should really be removed with a gravel cleaner. You can get a basic model gravel cleaner (see following link) from any pet shop or online and use it to drain water out of the tank and remove the gunk in the gravel at the same time.
https://www.about-goldfish.com/aquarium-cleaning.html
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API Accu Water is a flocculant and causes fine particles in the water to clump up and sink to the bottom. You don't need this. If the water is milky cloudy it is usually a bacterial bloom and doing a 75% water change and gravel cleaning the substrate will fix it. Most new aquariums also go milky cloudy for a couple of days after they are set up.
Make sure any new water is free of chlorine/ chloramine before it is added to the tank.
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API Quick Start is filter bacteria in a bottle. This is worth using. The best way to use this is to double dose every day for a week then stop using it. It contains dormant beneficial filter bacteria that wake up and start growing in the tank when they are added to the water. Try to add the liquid to the aquarium near the filter so it is drawn into the filter. However, it doesn't matter too much where it ends up as it will eventually grow in the filter.
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API Freshwater Master Test Kit is good and will test the water for ammonia, nitrite, nitrate & pH. Don't bother testing for nitrates until the tank has been run for at least 3 weeks. Nitrate test kits will read nitrite as nitrate and give you a false reading.
Ammonia and nitrite can be checked each day during the first month or so (depending on how long the filter takes to cycle), and then you check these if the fish look unwell or die or the water goes cloudy. You probably won't get a nitrite reading for about 2 weeks so don't worry too much if you only get ammonia readings during the first few weeks.
Keep test kits & water conditioners cool and dry, I kept my kits in a plastic container with lid, in the fridge. You should also check the expiry date on the test kits because they are sometimes expired when you get them.
*NB* Keep test kits away from children and animals. The kits contain some pretty toxic chemicals that can poison them.
Wash the test phials out under tap water after using them and wash your hands with soapy water after working in the tank and doing water tests.
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When doing a fish in cycle, you should only feed the fish a couple of times a week and do a 75% water change and gravel clean the substrate each day you have an ammonia or nitrite reading. You want to keep the ammonia and nitrite levels as close to 0 as possible. If you get any ammonia or nitrite readings, do a water change.
Make sure any new water is free of chlorine/ chloramine before it is added to the tank.
If you are adding a liquid bacterial supplement (API Quick Start) then just do a water change and do not gravel clean for the first couple of weeks. You can move the gravel cleaner across the surface of the gravel to pick up uneaten food and fish waste, but don't push it into the gravel until the tank has been going for a few weeks otherwise you can suck out the bacterial supplements.
Try to maximise surface turbulence/ aeration in the aquarium to keep the oxygen levels in the water as high as possible. This helps the filter bacteria grow and reduces stress on the fish.
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Sailfin mollies (Poecilia velifera) will probably get a bit big for your tank. And having 2 females, you will get babies in a month or so. Mollies are livebearers and produce live young about once a month. Female mollies that have been in a tank with males can carry up to 6 sperm packets that they use to fertilise batches of eggs without the male being present. They use one packet per batch of eggs so you could get babies for the next 6 months.
If you have plans on getting a bigger tank in the future, then you can keep them, otherwise you might want to look at replacing them with smaller fish like guppies.
Do not add any more fish to the aquarium until it has cycled. This will take about 4-5 weeks. During this time the ammonia levels will go up. After a couple of weeks the ammonia will drop to 0. When this happens the nitrite will go up. A few weeks after the nitrite has gone up it will drop to 0 and the true nitrates will go up.
When the ammonia and nitrite have both gone up and come back down to 0, and the nitrates start to go up, the filter will be cycled and you can add fish if there is room.
If you can post a picture of the filter we can tell you how to clean it.
