If you are purchasing this creature merely to practice on, what do you intend to keep if you are successful with this ?
I cannot understand why you purchased this Anemone. You have purchased a sun coral withut knowing how to care for it, you have stocked your tank without any cleanup crew and now you purcahse this anemone again with no idea how ot care for it.
It would have made far more sense to ask on here before your made such a purchase as we could have then told you just how diffcult these cretures are to keep.
Anemones grow large and providing it lives (which i have serious doubts) it will be so large that its going to endanger the corals near it. I havce made my views on anemone keeping on this forums many times and i feel very strongly about their care in captivity. I have one but it grew out of the liverock. I would never purchase one and certainly not to "practice " on.
As for placing it. The anemone will wonder all over your tank stinging everything in its path until it finds a location it finds suitable. If it doesnt find such a place in your tank it will continue to wander ovr your tank stinging everything until it dies
If i can give you the best advice available then its to ask on here before you make another purchase. You are their keeper and you are responsible for their welfare and health. Introducing corals and creatures that are far from beginners purchases is irrisponsible sorry.
Sorry if this is a little strong worded but i feel if you are to be successful in this hobby then its better to be honest right now before more damage is done.