Specifically, the web server process must have write permission to the script file. If you are not sure how to accomplish this, you can temporarily make the file writable by all users, and then revert to the current permissions when the setup is complete.
If you are using a GUI FTP client, it should provide the capability.
On UNIX systems, each file has three levels of permissions:
Each of these can have access to Read, Write or eXecute a file. If a file's permission string looks like this: "rw-r--r--", it means that the owner may read and write the file, while group users and everyone else may only read it.
For chatter2go to configure itself property, make the file readable and writable by everyone. Then, once the update is complete, simply set the permissions back to what they were.