Take it out of the pot, like so:
Cut the pot away with scissors or a knife carefully, then untangle the roots of the plant from the planting medium they use (typically looks like filter pad material). You don't really want the pot or material in your tank. Since it's water sprite, it won't matter much if you damage some roots, that stuff grows new roots and leaves very quickly. Still, being careful is always a good idea.
Hope everything is great with your new plants!