You can put AdSense at your Blogspot blog in 2 ways:
1. Add a AdSense widget. Blogspot have already this feature. Just add it (you must give your publisher id). However there are a bit less ways to customize them.
2. Add HTML/Javascript widget. Create ad at your AdSense account and copy the code. You have a lot of ways to customize your ads. You can also add channels and have better monitoring your ads.
