How to insert ads

Okay, first off, let me state that I have virtually ZERO knowledge of web design so please speak in layman’s terms.

I have my links all ready to embed but I just need to know ehere to put them. I am using the Easel theme for wordpress. The reason I am asking is because last time I went to edit theme and put the premade code in and screwed everything up. I had to work hard to get it back to normal. I kept getting that dreaded “can’t edit header” note.

So can anyone help to show me where I input my codes? I got’em all ready to go