Ready for ANAL!

So I am ready for anal me and my boyfriend do a lot of anal play when having sex like a finger or rubbing it’s very first stage for anal. I’ve started to enjoy it a whole lot and I’m ready to go allllll the way but I have no clue where to start and I don’t want him to end up with a dick full of my shit 😂. So what are some tips or steps to prepare to have anal for the first time?