Put a clear hose on the nipple and a container for the fluid to go into,then make sure the brake res has fluid pump it a few times then hold in on, then undo the nipple and close it (while holding the lever in) then pump again a few times and repeat the process until it bites, don't let the res empty of fluid always keep it topped up. Just keep doing this until u get rid of any air bubbles u can see in the clear hose.