How to use photoshop????

There are many available, just Google "basic photoshop tutorials" and you're off. Here's one I found that looks decent.

 

I suppose there are some tutorials on the web (in fact I know there are plenty). If you really want to learn photoshop, I suggest either buying a book on the subject matter or––even better––register for a training course. There are lots of useful features, even more so than putting your head on someone else's body, that you will be grateful to learn.

That's probably not the answer you were looking for. Good luck with your new application.