If you have a Wanner type gun, the plunger can be pulled back towards the bottom of the reservoir and then held in place either somehow with a proper Wanner you put one link of the chain into a little slot on the base of the gun, on rod type guns you move the rod sideways, play about with the mechanism to see how it works BEFORE you put any grease in.
Then (assuming the gun is empty of grease) the sequence is:
1. Remove the top of the gun from the reservoir.
2. Invert the gun over the tub of grease, centralising the reservoir over the hole in the plastic plate
3. Place the reservoir down onto the plate and hold it in position
4. Release the chain/rod from its latched position but DON'T LET GO!
5. Push the reservoir hard down onto the plate, forcing grease up into he reservoir, at the same time pulling the plunger back into the reservoir so as to give the grease space to move into. The idea is that you are trying to get grease into the reservoir but not air pockets.
6. When the plunger is fully retracted, latch it to hold it in position
7. Put the top back on the gun.
Last job is to expel any spare air, there should be a little valve at the top, you need to release the plunger to squeeze the air out.
In use, the plunger should be free to squeeze the grease up the gun. When you are not using the gun, lock the plunger to relieve the pressure on the internal seals of the gun.
Sounds complicated, but only takes a moment to get the hang of it.
