I Need Advice

So my boyfriend and I have been talking about trying anal for a while. He knows it’s out of my comfort zone, so when I told him I was okay with us trying it he’d take things slow. He’s very understanding with me and my insecurities, so he’s agreed to stop at any point if I get uncomfortable or just don’t like it. I’m just still a little worried about it all because it’ll happen in a few days. Could I possibly get some advice on what to do during the day before everything and what to expect during n after?