As explained above just fill the MC with fluid, push the plunger as many times as it takes to purge the air--- until there's no more bubbles. Pictures below show a dual reservoir setup but the principle is the same. You'll just have one return line/hose instead of two.
Then put lid on MC and make sure you keep it level until installed.
Matthew 6:33
1952 Chevy 1/2-ton 3100 Late '55 235/SM420/torque tube 3.55 Dalton Highway survivor (using original 216) www.truckwithaheart.com