How do I promote a player from the minors?

Begin by clicking the 'Promote/Demote' link on the Team page under 'Options'.  Your active players are listed on the left, minor league players on the right.  You can only have 25 players in the majors at any time; if you have fewer than 25 players in the majors, 'open' will be listed at the bottom of the list on the left for each open position.  If you have no open roster spots in the majors, you must choose which player you want to demote to the minors.  Click the buttons next to the player to demote and the player to promote, and then click 'Save Roster Changes'.