tcollier, welcome
you don't actually do any detailed managing, this game has some managerial settings, but your role is more akin to a GM.
Basically you draft a team based on a salary cap (real baseball, HA!). Rank then according to how important they are to you, and pick a stadium to play in.
Then when your league is full, that night (a little after midnight) the league will draft, and you will see what players you got. Note though that the replacement system is not like fantasy draft, where if you miss your first pick it goes to your 2nd. It will just give you the player, that no one else drafted who also plays the same PRIMARY position (listed first on the fielding chart) who is closest to the salary. So if you tried to draft ARod to use as a SS, and miss him, you would get the next highest 3B that is not on anyone elses draft card.
After that there is about 1.5 days till waiver clears. This gives all managers a fair shot at getting replacements for their team. You can make up to 8 waiver claims, and the order is determined by how many picks everyone missed.
After that the season always starts on the next Mon, with 3 games (1 series vs 1 opponent) taking place each night between midnight and 4 am. You can set your lineups, rotation, per game starters, and you managerial settings for closers, pinch hitters, how often to steal H&R, etc. There are more settings on the individual players.
Really it doesn't take much time to play. After the season starts, you can just kick back and let the team run (I don't reccomend that), or just spend some time each day (before 10 pm EST) to adjust lineups, pergame starters, settings, etc for the next nights games.