While you are in there, be sure to click on the following:
"Advanced Settings" link for hitters (this is where you set your fatigue levels, sacrifice bunt settings, Stolen Bases settings and all your options for whether players can be pinch hit for, pinch run for, lifted for defensive replacements and other things).
"Player Higherarchies" link for hitters (this is where you set who comes in to rest players, who actually comes in for defensive replacements, and your pinch hitters order)
"Advanced Settings" link for pitchers (this is super important as it sets your pitchers fatigue level, their target/max pitch counts, what inning they are available and such)
There are many nuances to the the game, but the advanced settings for pitchers is very important as fatigue for pitchers can completely derail your season. Simple rule of thumb, WIS gives you around* 15 pitches per inning for fatgiue purposes, so you can use this a guage based on your estimated number of appearances to determine pitch count settings.
Read up in the forums about the tricks of the trade. http://www.whatifsports.com/forums/Posts.aspx?TopicID=462961&TopicsTimeframe=30
is a great forum with many links to some of the best game advice on the site.
Welcome and good luck.