I typically seek to use a three man rotation for my starting pitchers. I have found that I have to use pitchers that have at least 250 ip. I am trying to figure out how to keep the three man rotation while using Martinez 1.74 217 ip or Maddux 1.63 23? Ip. I want to start one of these pitchers in tandem with the 1.63 Clayton Kershaw. I can't figure out how to use the advanced pitcher settings to get this to be effective. I can see from other people's lineups that it will work, but I need a little help with how it works. Any advice?

Tandem pitchers generally need to be the last spot in a rotation unless you're using them in all of the rotation spots. I've used both combinations you've referenced in your post. The pitch count for the starter and the reliever should reflect 54 appearances as part of a 3-man rotation. I like to set the reliever to require rest at 99% so that the sim will rarely use him other than as a tandem with the starter. It's an expensive option but it can work well.

Do I read that correctly as a 3-man rotation with '00 Pedro/'95 Maddux paired with '16 Kershaw in one slot?

That would be easy.

Starter #1
Starter #2
Tandem 3A - Maddux or Pedro
Tandem 3B - Kershaw

Maddux and Pedro can throw about 65 pitches per game as part of a 3-man rotation. I usually set them at 60/65.
Kershaw should be set at 40/40 since that's really all he can throw in a 3-man rotation. I've got him at 42 pitches per game over 54 expected games.