How to restore backup without replacing?

Hello,
First off, sorry if this is in wrong forum? It seemed like the right place, but not sure.

This is the problem I am having. For school, I needed to get Adobe Creative Suite 6 onto my Macbook so I can work on specifically Adobe Photoshop and Illustrator. So that was all fine, but then Adobe Illustrator wouldn't open, it would throw up error messages, so I decided the only way to fix it would be to wipe the Mac clean and restore it. I bought an external hard drive, backed up the Mac, wiped it clean, reinstalled using the Mac Installation DVD and reinstalled Adobe. Good news- it works! But now the problem is, I have a clean factory-condition Macbook with Adobe CS6 and nothing else, and I need to restore my old data from my external hard drive onto the Macbook without deleting, altering or replacing my current files. I don't want to just restore it because I think it will just rewipe my Mac and restore it with my backup that was fine except it didn't want to install CS6.

I've looked all over the internet, but many people are vague and I don't know what to do! Please keep it in lay-man's terms, and I hope you can help me soon. I need my old files for school, and quickly.
Thanks again!

 

Oops, probably should have specified further, I had done absolutely all I could do. I googled everything I could, but no one seemed to know about this error, even the Adobe developers couldn't figure it out, so after all this file deleting and Terminal fiddling and all this hoohah, then I wiped.

I did have a look at Migration Assistant, but I'll have another look tomorrow, but that sounds like just what I need! Thank you so much for your time!