How to Reformat this computer

Usually I don't have problems with finding information or just learning how to do things my self, but right now I'm having trouble reformatting my computer. Of course I have never played around with a computer this new. Im just not used to the way it is set up. Im used to the old way things were set up. Any way if anyone can give me a little help on starting the reformat process I would really appreciate it.

 

Thanks

Mr.Glass