I don’t believe the official plugin supports sidebar ads. On College Confidential, we added ads in the theme using essentially a background image:
We also used OptinMonster to slide in ads.
Ads on the left sidebar don’t seem like a good idea for sites that use the Sidebar navigation. Sidebar ads don’t work on phones either. The right sidebar seems particularly prone to banner blindness. Still, it would be useful to have that space available for ads if only to support popular ad sizes.