Fill out the appropriate online form, giving your Columbia address as your residential address*, which will give you a PDF to print and sign. Email the signed printout plus a copy of the front and back of your Missouri driver's license or other acceptable ID to Clerk@boonecountymo.org
*If you feel strongly about registering in another Missouri jurisdiction, but you wont' be present in that district on November 8, be sure to present your Missouri photo ID when you register, or present that ID there between now October 31, the deadline for requesting an absentee ballot. You will not be sent an absentee ballot unless you showed someone an acceptable photo ID at the time you registered. Scanned ID (front and back) may be acceptable as well, but check with the county election authority. If you want to vote absentee in another state, check procedures there. Be aware that many states, including Missouri, require you to get your absentee ballot notarized before mailing it in, so you must build in extra time. If you are uncertain of whether you will be required to vote in person, call your election authority.