I couldn't find the post for it.
I am new to the plant tank world.
I was wondering how do you cut the plant and re-plant it in your tank.

depends on the plant.

I believe as I look at mine that you have to wait till it puts out a baby from the bottom, or till it puts up a flower spike. Mine put up two spikes recently and had little babies growing from the stem half way up complete with roots. That's how I'm getting little ones for my new tank.