Being overseas doesn’t exempt you from voting, it just means you have to sign up for an absentee ballot. It’s too late to register as absentee for the November 4th Election, but make sure to do so for the next election. Check out Go Vote Absentee to figure out how to register as or change to absentee.
Even if you’re at home for the elections, I strongly recommend you vote by absentee ballot. Voting by absentee means you get your ballot mailed to you a couple of weeks before the date of the elections, so you can avoid the lines at the polling place and fill out your ballot at place and time of your convenience. I find voting by absentee especially helpful since I can research candidates and issues on google with my ballot right next to me.
If you are abroad, you can either mail your ballot or drop it off at the US Embassy. Yesterday, I dropped off my absentee ballot at the US Embassy in Edinburgh, and it was surprisingly quick and hassle-free.