You can register to vote any time up to and including election day. This is commonly referred to as same day registration. In order to register you must bring 2 forms of identification to the polling site. One piece of identification must be include your current DeKalb County address.
Information on election day voter registration can be found here. Note, this may not be the normal polling place for your precinct.
Early voting has already begun and is easy to do. If you’re not registered you can even register and vote at the same time. Sample ballots, polling locations, and more information can be found here.
Sample ballots and election day voting locations specific to your precinct can be found here.