Go to the computers tab in parsec, and click Share Button underneath your computer (If you do not see anything, click the Reload Button in the top right). Now that you have XCOM running, you should see it on this list, put a check next to it to enable your friends to later see your game, and nothing else, when they join later. Tab to, or use the Parsec overlay, to go to the Parsec Setting> Approved Apps Tab. Start up XCOM 2 and/or WotC while having Parsec running. Download and install the Virtual Audio Cable fix here *. Super easy once you've done it a few times, but the first time seems daunting. First time setup, and testing to make sure everyone can join, WILL take some time. Remember, you're going to be streaming to maybe up to other five people- you can't do that on a potato computer and a dial-up modem.
The best internet connection/computer out of your group of friends.