If you have a question about voting, don’t hesitate to contact whichever department handles elections where you live. In my experience (in the USA), they’re helpful. If you don’t know where to get started, try searching for your state name and “elections” and you’ll probably find the right site. Look for a .gov, go to that, and click on anything that says “contact.”
You can find many answers to questions like “How do I register” or “Where do I vote?” with a quick search, but maybe your situation is a little complicated. Maybe you’re a student and your license says you still live at your parents’ house, but you’re now living in a different place close to your school. If you hit a wall in your research and aren’t sure what you can do, don’t give up. Just ask.
In one local election, I had received my ballot by mail. I didn’t plan on voting, so I didn’t send it in. I think I shredded it. On Election Day, I wanted to vote. I called the voter hotline. They answered right away and were super-friendly. I asked if I could vote, and they explained that yes, as long as I was registered to vote, I could go to any polling location and request a provisional ballot. As this was in California, I was also able to see if my ballot was counted after it was confirmed that I did not cast my ballot by mail.
In a national election, I knew that I was going to be moving to a different state before Election Day but after the new state’s registration deadline. I did some searching, but wasn’t quite sure how I could vote. I emailed the elections division of my current state and explained my situation. They replied noting that under 52 USC § 10502 I had the right to vote for the offices of President and Vice President, and guided me through the process of obtaining an absentee ballot. At one point, I contacted the wrong office and they simply brought the right person into the conversation, so don’t worry if you don’t know exactly who to contact.