Prep 4 Anal?

I want to try anal with my boyfriend. He kind of had planted the idea of anal in my head. Since today is day one of my period I figure we could have anal while I'm on my period since my other hole is bloody occupied. How do I prepare properly for anal? I don't want there to be poop every where! Let me know or imma have to tell my boyfriend that I am super tight butthole and that shit just ain't working out. Lol. Literally!