Subject says it all… Im kinda a newbie so please give me a step by step guide :). Thanks 
Find an object with a hole in it, put a hole in an object, or find any object at all, then tie a string to it.
Optimally you want it to be about 9-10 grams, or between 1/6 and 1/7 of the yoyo’s weight. A bouncy ball is the cheapest thing you can find lying around, 1" dice would work but you’ll have trouble finding one.
If you don’t have a drill, get some clay, find out how dense it is, and get creative.
I have a great one that I made myself. Using old strings, a pen tube, blu tac and some white glue mixed with water.
Just PM if you want more details.