Eligibility depends on many factors, however, the most important one is that you must hold assets in at least one of the issuers available in the market.
Currently you are only able to create sell requests for eligible SAFEs from companies that have previously raised on Republic. Most assets have a lockup period of about 1 year before they are eligible to be sold. Issuer approval for secondary trades is required for a sell requests to become active and available for purchase.