There are many ways to make friendship bracelets. I don't know if this one has a fancy name but we can just call it a friendship bracelet to make everything easy.
What you need:
String (this can be hemp or bamboo cord or whatever!)
A safety pin
How to do it is pretty simple. First measure out some string. I usually do 2 1/2-3 lengths of my forearm. I don't really know how long that is, let's go with around 2 ft.
Taking the left outside string, make a four shape crossing the string over the center strings.