Nice piece of wood, lot of options on what you can do with that in a tank.
But, making the wood waterlogged and staying down can take a little while.
What i normally do with any new pieces of wood is firstly to pour boiling water over the wood to get rid of any potential nasties and give it a good scrub, and pour boiling water over wood again before i put the wood in a suitable sized container filled with water with just an airline to give a little flow and aeration to the water and tie wood to usually a rock and sink it. And change the dirty water for clean whenever it requires it. I usually put his container out of the way into a cupboard or something so it dont looks messy and clutters up the room for whatever length of time it takes.
The advantage of doing things this way, it won't mess up the tank with tannins and bits of wood everywhere, even though the tannins are beneficial to the tank, many folks don't like the look it gives to the tank water.
It can take anything from several days to weeks, even months before the wood will sink on its own, this does depends on the the type of wood.
Its worth doing, as you know the wood is safe and leached of all bits of wood and tannins. of course will look great in your tank