Attempting anal for me and him

So my bf and I are working our way on getting kinky and we’ve decided to try anal.

He says that it’s fair for me to do something to him if he does it to me. I was thinking just trying a finger for him, but like how do I go at it? Should I have him bent over or like when giving him a bj? And how do I do it so it feels good for him?

I’ve never done something like this

Also, what are good positions while trying anal on my part??