Perhaps the quickest way for inserting a Google Ad into a blog based on WordPress is by using a Text Widget.
This method is viable on any blog with any template, provided the latter offers at least one sidebar.
To implement it, first of all select the Appearance/Widgets entry in the admin area.
Then you have to drag a Text button from the Available Widgets area and drop it into the configuration area devoted to the sidebar you desire.
Now you need to type (or copy and paste) your Google ad script, which you generated on your Google account, in your Text widget body.
Just see the following example:
WordPress Text Widget Google Ad Script example
and how the Google ad in it looks like on the web.
