Question

My class is doing a unit on the "completing the square method" which is used to solve quadratic equations. I need help understanding this method. It's not making any sense right now! I have two problems and I need to figure out which number completes the square. Here are the problems:
1: x^2+8x
2: y^2+10y

First one: Take one half of eight, and square it: 16
Second one: take one half of 10, square it.