Adding code for ads or other sites (newbie when it comes to code issues!)

I haven't found this question in the forum so here goes: A tech person from my web host had to help configure my header image by going into my Cpanel. I had no luck working on it myself as it apparently had to be done through the host, and not by configuring the theme or by my connecting somehow with WP.

Now that I have the basic blog/web site up and running, I've hit a wall and don't know which aspects of Atahaulpa that I should be able to configure directly or if they're Wordpress issues like the header that for some reason must go through my web host into my Cpanel.

I'm ready to monetize, but can't figure out how to use the widgets,
or even where to put code for a web site directory that tracks stats. I tried pasting code for google analytics into my editor and it didn't work - thought I put it in the correct place.

Is it necessary to edit the code in the editor, for instance, to make connections with advertisers?
And if so, I can't figure out how the widgets work.
Sorry to be so dense! I know there are various issues raised here.