Here are some basic guidelines to follow to purge your Brite tank (or similar vessel) with CO2 before you fill it.
First, your Brite Tank should already be cleaned and sanitized at this point, if you haven’t yet done this, please refer to our articles on the subject!
For the Brite Tank, the best method is to fill the tank entirely with water and a no-rinse sanitizer then close it up and use a couple of psi of CO2 to evacuate the sanitizer mix so that the entire volume is theoretically filled with CO2. You’ll then vent off the positive pressure before filling and just barely crack the lid and begin filling the Brite tank with beer from the bottom.
Be sure to check our Pressure Transfer/Kegging Guide for more details on transferring beer and other beverages between tanks.