Solution
Xfce is already installed on cRIOs running Linux Real-Time as the embedded UI, so you don't need to perform any additional installation to open the program. In order to launch Xfce on your cRIO, you will need to SSH into your cRIO using
PuTTY or a similar SSH interface, and use the below command to launch Xfce:
startxfce4 > /dev/null 2>&1