You can train pretty much any animal at any age, so start now! Both of mine can stand up and spin counter-clockwise, and generally come when called. They’ve worked on jumping over a box as well. More practically, I have trained Otto to let me handle a bit more than he would normally tolerate. He can sit on my lap and let me hug him though he’s a very non-touchy rabbit generally. It’s helped him settle down with handling and nail trims (though he still doesn’t enjoy them, just tolerates them).
I would also recommend a clicker. Bunnies aren’t really evolved to work with humans and read our cues the way dogs do, so using a clicker is a great communication device to help them understand exactly when they do what you want.
Another thing to keep in mind is that bunnies generally respond to body language better than verbal cues (which makes sense since they are generally pretty silent in their own communication with each other). Between my two, one pays some attention to verbal cues, but the other has absolutely no idea that words mean anything, so body language works best for them.