How do girls pull there pants down to pee in the woods?

You don't. This can be considered sexual harassment and is illegal.

Depending on her personality, pulling a girl´s pants down could either turn her on or turn her off. If you don´t know her well enough to be sure what her preference is, you could ask her.

Grab their waist. Put your fingers through their belt loops. While they're distracted pull down really hard.

If you are a girl and need to pee in the woods I say find a tree unbotten and unzip your pants and pull your pants and panties down to your knees and pee on the tree.