Figured I'd put out a quick video and text tutorial for how to install the RC candidates since it strays a bit from the Dev Branch switching outlined in Dwarden's Sticky:
For anyone not familiar with the process, dwarden blasts out details for a Release Candidate build and test server details.
He does this on the skype channels
and on his Twitter
In order to switch to the RC Branch, follow these steps:
Step 1. Right click on Arma 3 in your steam library
Step 2. Select Properties
Step 3. Go to Betas tab
Step 4. Enter the password provided by Dwarden in the "Enter beta access code to unlock private betas" text entry area
Step 5. Click "Check Code" button
Step 6. Select the relevant RC from the dropdown list
Step 7. Wait for update files to DL and patch
Step 8. Launch Arma 3 and select "Play" and then "Multiplayer"
Step 9. In the Multiplayer server browser select "Remote"
Step 10. Enter the IP address provided then enter the port number provided
Step 11. Return to the server browser and you will see the test server double click on it or select it and click "connect"