I need some tips on how to tell a new partner about sexual abuse?

Pillow talk: After intercourse can be a time for the most intimate sharing. "mmm... When i was a kid, something really bad happened to me. I am glad that with you, i feel safe and happy. Thank you." even better -- if past experience still imprison you (and they may not, and then it's moot), a short course of psychotherapy by a competent person can set you free to love and be loved as you want.

Honestly: when you feel enough trust and safety with the person. Tell your story and if the person cares about you then he or she will listen without judgment.