Inserting ad code when using adsense plugin?

I just can′t figure out from the instructions if I have to manually insert the ad code if I use Adsense by Google as a plugin in Word Press? I′ve tried to paste the code in the (html?-)text-field when editing posts (not “visual”), but the code don′t show when I open the page (in another broser) and view the source code. Then, I′m thinking that I might have to use FTP….(?) But then I can′t find the files containing the posts or pages, just (word press) themes and such.

Am I thinking right or wrong?

Steffen.

https://www.ads-software.com/plugins/google-publisher/