A couple of ways:
1. use an Adsense plugin.
2. put the Adsense code directly into the WP theme files.
Myself prefer changing the WP them files, because doing that we have more control and easier to change in the future.
Just be careful if you are putting adsense units into posts. From memory adsense TOS allows only three ad units per page.
I would suggest that you use the Adsense Injection plugin for your blog. Fast and simple to setup.
– MENJ
Where do I get an adsense plug-in?
Start with Plugins – look in the commercial (I think that’s what it’s called….) section.
