Hi I was saw this post as I quickly looked over Zach's shoulder, along with another post, and I thought I'd help out as I went through this recently. Well personally one of the most important thing is being relaxed, I've found that a nice warm/hot shower or a nice warm soak in the tub will help. Maybe a backrub, you want to make sure you're completely relaxed, granted once you've been doing it a while, you'll be able to slap on some lube and take it, slowly at first of course, but it's much easier if you're relaxed. If you're worried, get in the tub, put the water warm, but not scalding of course. Use soap, or some sort of lube (I use my soap, but mine isn't one that would burn if I did) and play with yourself back there using your own fingers. It'll help ease you into it. Once you're comfortable with that, move up a toy or something of the sort, and from there try his penis. Well hoped that helped. Have a good night.