Hmmmm. Do you mean writing original songs? That would involve quite a bit of guitar knowledge and a good imaginination. Mixed with half a cup of creativity, you have yourself the recipe for success. Hmmmmm, that was weird. Anyways, just start playing something and see if you can't find something you think sounds cool. Even just a chord you think sounds cool. Work off of that and try to piece something together. Hope this helps, and good luck.