For an exhaustive set of links with all kinds of voting information from the State of Idaho, follow this link:

http://www.idahovotes.gov/vinfo.htm
Register to Vote through the Mail

Registering to vote in Idaho is easy. If you're eligible to vote, just follow this link, fill out the form, and follow the instructions. If you haven't done so yet, DO IT NOW! Don't wait until it's too late.