If you have signed up to vote by mail in Arizona, your ballot should have arrived by now. The Pima County Recorder's Office mailed the ballots out on October 7, 2020. Be sure to check your mail for a large, pale-green envelope. If you do not have your ballot by the end of this week, be sure to follow up. You can see the status of your ballot at this website.
As soon as you have your ballot, fill it out and return it. Ensure you follow all the instructions, to the letter. Any error could result in your vote not counting.
Mailing your ballot back is probably safe. If you want to be more certain that your ballot will reach its destination, you can also drop it off. You can take it directly to Pima County Recorder 240 N Stone Ave Tucson AZ 85701. More drop-off locations will be available, but not until October 19, 2020.
However you do it, make sure to vote. No one can sit this one out.