I have two pitchers with 415+ innings and a 3rd with about 150.  How do I set up the 3rd pitcher to go every 5th day?  Thanks!

Not sure why you'd want to do that. I'd just use two starters and put the other guy in the pen.
Anyway, if thats what you want, the only way I can think of is setting them as Starter 1,2,and 3, and using fatigue to designate their starts. You'll have to calculate pitch counts pretty close, and give them all a '1' pull setting so they hit their pitch count consistently.
The first two pitchers will play in 65 games each, so 415/65*15=95 for their pitch counts. 150/32*15=70 for the other guy. The third starter will be skipped ever other time because he will be too fatigued to play. Make sure your autorest setting are set.

I'd also throw away the first couple of games with scrub starters, because this kind of setup is really hard to control fatigue-wise. You may have to adjust those PCs up or down by 5 depending on how their fatigue goes throughout the season. GL.

Thanks, BL.  Still learning the ins and outs (as noticed by my record in league 91791--you lead the East and I am last in the Central).   I have tweaked pitch counts and brought up an absorbo from the minors to start game 3.  Actaully, my absorbo has decent ratings (8-5-6, stamina of D) so I set him at 65/75 for pitch counts.  Will see how he does.