New Balance N4 heart rate monitor help

I read a few posts on here regarding the hrm and bought it last week. The manual was not informative so I was able to set it up from the helpful posts of MFP members but I am having trouble clearing a past workout and saving a new one. I managed it once but then I did an insanity workout and at the end was excited to see my calories burned but it only showed the workout from the other day. Any tips?