Make certain your Roku is on the wireless network using the "MIT" wireless SSID.
Using a computer, you'll have to create a free account at Roku Free Account Creation (no payment method required) as the first step. That account name can be anything, and does not have to use your MIT email address. Then follow the procedure for pairing the Roku with the account.
Note: Roku will ask for a payment method if you try to register directly on their site. There is no charge associated with using the Roku for Xfinity On Campus, so you do not need to register with a payment method unless you plan to purchase paid content.
Once on the network, go to the menu which allows you to search for available channels. Search for the "Xfinity Stream Beta" channel app, and install it.
Start the Xfinity Stream app, and acknowledge the startup screen. You should then be presented with a 6-digit number.
Visit the URL indicated (xfinity.com/authorize) using a web browser, and enter the number. You should then be presented with a login screen.
Select the LAST option, "for xfinityoncampus users", and then log in with your MIT credentials.
After a short delay, the TV display should change to show you an enduser agreement. Press the down-arrow key on the Roku remote four times to highlight the Agree button, and press OK.
Now you should be at the home screen for the app. Press OK on the remote to get to the guide for live TV. The "*" button on the remote will allow you to search for channels by number or name. MIT users also have access to on-demand content.
Fully illustrated instructions are available at the XfinityOnCampus.COM website after you log in.
All current models of the Roku are supported. You can find out what those are at the Roku.COM website. If you plan on using the Roku with an older TV which does not have HDMI, you will need the Roku Express+ model, which has analog A/V outputs."