So, when I shift the car from inside, nothing happens. The cable is messed up and I don't know if it needs replaced or if it can be fixed. If I hold a piece of it, it can be shifted just fin from inside.

it's that black piece shaped like a cylinder. It's loose and not connected to anything. It runs freely on the cable. How can I hold it in place?

 

That black cylinder is supposed to be attached to the bracket. I'm guessing that part of it is still in the bracket and the floating piece has broken away.

You need a new shift cable.

Edit: See the first page of the attachment.