these oil pumps are supplied filled with oil and pre-bled but if you wanted to double check you would...
1) loosen and remove the bleed screw on the pump until the oil runs freely (this bleeds the oil supply from the tank which uses the larger pipe) then refit the screw
2) disconnect the small pipe where it normally attaches to the carb and tick the engine over to make sure oil comes out the small pipe (do not rev it)- it will come out in pulses, maybe one small pulse every couple of seconds- if oil does not start to come out within a few seconds you'll need to stop the engine and run it on pre-mix for a few minutes until it bleeds itself through and pulses out consistently- then reconnect the pipe and switch back to neat petrol- alternatively you can just spin the oil pump gently with a battery drill (with the large pipe connected to the oil tank- make sure you spin the right way) until the oil comes out the small pipe consistently and then connect to carb before starting the engine