If you have just been admitted to the AdSense program, you're probably excited about finally being able to enable ads on your site.
Unfortunately, the documentation around showing ads isn't quite complete for the Blogger platform. Here's what you see in the 'Earnings' section:
So it seems like if you want to show ads below posts and on the sidebar, you should select the first option, right?
Not quite. To enable ads on the sidebar, first, you need to add an AdSense gadget to the sidebar. Otherwise, after a day or so, your selection will revert to 'Only show ads below posts'.
Once done, you will be able to display ads on the side and at the bottom of your posts. My experience has been that by doing so, you can increase your ad revenue significantly compared to just bottom of the post ads.