You can register to vote at any time. The deadline to register to vote for an upcoming election is 29 days before the election.  

The Sumter County Register to Vote website has an online registration form and instructions for submitting it to your county’s Supervisor of Elections.

STUDENT REGISTRATION
If you are a student in college in Florida, you have a right to register to vote at the address you consider the place where you live, whether that is your family’s home or the place where you attend school. You should update your registration anytime this home address changes.

FELON VOTING RIGHTS
A felony conviction in Florida for murder or a sexual offense makes a person ineligible to vote until the person’s right to vote is restored by the State Clemency Board.  For any other felony conviction, a person is eligible to register and vote if the person has completed all terms of his or her sentence. 

The Florida Division of Elections website contains further details.

However, determining whether “all terms of a sentence” have been fulfilled is not as straightforward as it sounds.  The Florida League of Women Voters provides resources to help returning citizens determine their eligibility.