Season runs August 1 to February 15. Bag limit is 5. If you are planning on hunting public land, check the site-specific rules (It's under the Hunting/Trapping tab listed as Public Hunting Areas). Not all public sites have squirrel seasons, and some have limited seasons or other restrictions (shot gun only is a common restriction). If you have any specific questions, I'll try and answer them.
You can download the Hunting Digest on the IDNR website, and there's some info in it.