I need help with creating a "user account" website (i.e. Facebook, Twitter, etc). I have a home page set up, i just need to have the it jump to the "user's profile page" once they login their credentials (username, password). I know it has something to do with MySQL/PHP.

Can someone help? I'd appreciate it.

I know it has something to do with MySQL/PHP.

This comment gives me enough to know, that you don't know enough.

Maybe you could do something with one of the existing solutions that they list on this blog.
http://fossbytes.com/how-to-build-your-own-social-networking-website/

Otherwise, you would be putting the cart before the horse, and you should really be learning the basics first.

The question is ::

I have a key
will somebody build me a car that fits it

At this level of knowlege perhaps wordpress or other prewritten blogware and the user control plugins