The basic principles are simple.... squares for men, circles for women, connecting lines, cancelled lines for relationships, crosses across the square or circle if the person is deceased, and as much information as you need re ages, names, for the problem you are trying to solve.
www.edrawmax.com/genogram/how-to-make-a-genogram/
https://www.orgcharting.com/how-to-make-a-genogram/