Where to insert google adsense codes?

I know there’s programs out there that supposedly help with this and I’ve downloaded them…but I don’t know where to put the code that Adsense provides me with in terms of the content, search, etc. ads. I’m trying to put some horizontal above my header, as well as some in the sidebar, but I have no idea how to do this or where the php files are located that I need to place the code in. Please help!

Also, is there a way to get placed higher in google searches?

Thanks!

E.