A candidate wishing to be on the Presidential Preference Primary ballot must submit a petition including 1,000 signatures of registered voters, they don't have to be registered as “affiliated” to sign the petition.
The deadline it submit the petition isn't yet known.
If you registered to vote as “affiliated” with a particular party, you may only vote in that party's primary.
Although if you registered as “unaffiliated” or “independent” you may choose which party's primary to vote it, which then “affiliates” you with that party.
The Primary is on April 28, 2020