assuming your clean and everything enema etc ..
1.lay face down ass up (position may vary per lady)
2.relax your ass muscles
3.squirt ky jelly in your ass, lubricate your fingers/his or toy with ky jelly & slowly insert in and out , keep lubricating using up half of the ky jelly bottle
4.until your comfortable, then your ready for sum real dick, using the rest of the ky jelly lubricating his dick and your ass and like someone said before try a small dick first
did it with my ex wife like this and she loved it !, she had never done it before & she said it wasn't painful like this ! ..took us like 30 minutes before we got a good rhythm going, we used up the whole ky jelly bottle , that's the key and slow
have fun !!!