To register to vote click on the link and download the form to fill out.
You will have to mail the form to the county courthouse at:

Macoupin County Courthouse
PO Box 107
Carlinville, IL  62626

If you have recently moved, you must change your address in order to be eligible to vote in the next election. (Remember that there is a 28 day cut off prior to any election that voter registrations cannot be accepted.)

Link to Voter Registration Form