I really like the clothes for young Adults in University, but are they available for adults as well? If not is there a mod or download or something to make them? Actually, I think you just need simPE. Is there a tutorial to tell me how to make clothing into different ages on simPE?

Young Adults and Adults have exact the same body mesh, so you should be able to make them available for both without any problems.

There is a tutorial, because I've used it, but I can't remember it. Maybe search under the tutorials here.

They have to be enabled. It's easy enough with SimPE and Bodyshop - Tutorial here: http://modthesims.info/t/122944

If you don't want double copies, you have to extract PropertySet resources from the University files. It's a bit harder, but very much worth it, as there'll only be one file instead of several.
Path is C:\Program Files (x86)\EA GAMES\The Sims 2 University\TSData\Res\Catalog\Skins
- Open the "Skins.package" file in SimPE - Right-click the Property Set resources you want, choose "extract" and save them (without changing the filename) in a new folder.
- make a new file (file -> new)
- Right-click inside the empty resource list and choose "add..."
- Select all the files you want
- Change the "age" line to 48, or 58 if you want elder too (40 for YA, 8 for adult, 10 for elder --> add them up whichever way you want). Elders will get an adult body, so if you don't want that, stick to "48".
- Click "commit" after each change, and save the file with a new name
- Don't change the original "Skins" file.

For downloaded clothing you can use the wardrobe wrangler --> http://forum.jfade.com/viewtopic.php?f=11&t=457

You can check out this mod : All Adult/Y.A. Clothes made available for Young Adults, Adults, and Elders - https://www.modthesims.info/download.php?t=288078 . With this mod, all my adults (and elders too ) had full access to Young Adults' clothes.