How do I hide the yarn in back of a stamped cross stitch quilt kit?

I bought a pre-stamped cross stitch quilt 20 yrs ago for my daughter and completed it before she was born. She is now married and has her own child on the way, I'd like to do this again for her child. It's been so many years for me that I have forgotton how to hide the knot, or do I not do and hide the thread? If so, how do I start off? Any help would be greatly appreciated. Your advice is very much appreciated by this new granny.