Lol been here and got the T-shirt,
Do you have an internal filters or powerheads lying around that have the same diameter outlet as the hose on the external?
If yes attach the internal filter to the inlet hose, and turn on the internal so that it is pumping water through the external, once the external is full and water is flowing throught the spray bar simply turn off the internal and turn on the external,
If the above isn't an option take the outlet hose and hold it as high as possible, add a funnel to the end and fill it with water until the cannister and hose is full of water, then aim the outlet over the tank and switch on the filter, hopefully it will work but if not give this method another couple of trys, It does usually work after a few attempts