In real life, all prospects born in Canada, the United States, Mexico, and any U.S. territory, for example, Puerto Rico, are eligible after six consecutive years in the minor leagues without a promotion to the majors or a failure to be added to the 40-man Roster. For international prospects, they are eligible after four years of service. During the offseason of your franchise, there will be a list of eligible Rule 5 players that you will have to choose to add or accept to your 40-man, or decline, and leave that player unprotected, to be eligible to be drafted by any team. Click that button to perform that action and choose those players that you want to keep, if any. I hope this helps you understand this process and makes this easier for you.