You can install PSI by visiting the PSI Homepage and downloading the appropriate version for your operating system. For Mac OS X and Windows, you simply need to double-click on the file, once it is downloaded, and follow the on-screen instructions like a normal install.
1. When you start PSI, you will be presented with a screen to let you set up your "account". PSI supports multiple jabber accounts, so you will want to name this one so that you will remember that it is your account here in the CS department.
2. Next, you will need to set up your account's details. Your "Jabber ID" is: NetID@jabber.cs.uiuc.edu, where you should replace "NetID" with your own NetID. Your password is your Active Directory password.
3. You will need to make some changes in the "Connection" tab, as well. Make sure that "Use SSL encryption (to server)" is checked, as well as "Allow Plaintext Login".
4. When you're done, click "Save", and you will be presented with the following screen. Right-click on your account name, choose "Status", and choose "Online".
5. Now you are logged in to the Jabber server. Depending on your role in the CS department, you may already have some contacts added to your contact list. To add more people, right-click on your account name and choose "Add a contact". All accounts on our network can be referenced by their NetID@jabber.cs.uiuc.edu.