I downloaded the CB plugin and when I tried to install it on CB it would not let me.

These are the two messages that appear:

ERROR: Could not find an XML setup file in the package.

Installation file not found:
/homepages/................................................................/install_4d756dd29046a/

Any ideas on what is causing this to happen?

If you were trying to install FreiChatX as a CB plugin , then
let me tell you that its not a plugin but a , independent chat system

You should read the readme file provided in the zip archive .
Almost every software has a readme file in it.

You will get the installation instructions in it.