I had a slave for a long time that had never had a climax in her life. Strange but she loved sex at least with me.
Here is what I did to help her. Mood music, candle lights, gave her a bath soft and slow, a little pot, then out in front of the fireplace with a lovely warm fire going I spent time with a piece of fur and then my tongue exploring her body. Then came nights of licking her clit while touching her lightly till she finally had one.
Her problem was she felt masturbation was a sin so had never taught her body how to cum. That may sound funny but it is the truth. Get a vibrator or 3 and practice alone if you have too. Once the body gets the hang of it, it will become easier and easier. Use your mind or your favorite porn to help you when alone.
Russell