If you don't have it by now it's too late. As mentioned, you can look up your county's board of election website and find out their hours for voting "on demand" in person prior to election day (limited options left, probably just Monday).

If your ballot does arrive, you will want to complete it ASAP and take it to a drop box - not put it in the mail, as a postmark is insufficient. It must be received at the Board of Elections no later than 8pm on election day.

Other option is to vote in person on election day. If you get your ballot in the mail beforehand, bring it with you. The judge of elections will spoil it and you'll vote in person as usual. If you don't have it, ask to vote provisionally. That means your ballot will be segregated and will only be counted after they confirm that you did not vote by mail. Insist on voting provisionally if you are told you cannot. Anyone and everyone can vote provisionally in these situations. However, best to not vote provisionally if you can avoid it because there is a high standard for the BoE to accept a provisional ballot to prevent people from voting more than once.