First things first; safety measures
Always make sure that the tufting gun is turned off when threading it. Preferably unplug the machine, that way you cannot turn it on by accident.
Also unplug your tufting machine when changing/replacing any parts.
When changing the scissors of a cut pile tufting gun, do not forget that it is sharp. Be sure not to cut yourself.
Never touch the moving parts while tufting and make sure that nothing (like your hair) can get stuck in the moving parts.
Threading your machine
Regardless of the tufting gun model you bought, the machine has two "eyes" that need to be threaded, one at the top of the machine and one in the front of the needle.
You can thread your tufting machine by putting de yarn first through the eye on top and last through the needle. It is easiest to use some kind of needle threader.
This youtube video shows very clearly how your loop pile gun should be threaded:
It is easiest to use some kind of needle threader. If you have some kind of iron wire, like a paperclip, you can fold it flat and then fold it double to help you guide the yarn trough your gun.
It usually works best to feed as many threads as you can fit without it getting stuck.
Again, make sure you have a proper yarn feed so the yarn cannnot get stuck in your machine.
If you have your tufting set up complete, with a tufting frame, a well stretched tufting cloth and proper yarn feeding, you can get started with tufting.
The gun only works in one direction, so if you want to do horizontal lines, or diagonals, you need to turn the whole machine so that the needle works in a straight line.
If you just started tufting it is easiest to work in lines from bottom to top so you do not have to turn your machine. As soon as you get a hang of it you can try other directions.
When you are working with a loop pile tufting gun, you need to cut the yarn at the end of each stroke/line by hand. For the cut pile tufting gun this is not necessary.
Your tufting gun has a "foot". This foot runs over your cloth and helps you apply consistent pressure. You can press your gun into the backing cloth so that the foot leans on the cloth.
When applying to little pressure your yarn will not get stuck in the cloth and you even risk that the scissors of your cut pile gun cut the cloth.
Changing from cut to loop
For the cut and loop gun you can find instructions to change the cut pile head to loop here (or loop to cut).
The tufting guns require some simple maintenance. Mostly it is just a matter of keeping the machine running smoothly by adding a drop of (sewing machine) oil to the moving parts located at the blue arrows. Do this at least every month. The first arrow is for the scissor of a cut pile machine.
When you use a cut pile machine, the scissors might need sharpening or replacement over time.