You'll just need a fair whack of air for it to run.
A 2.5HP can get them going for a little bit but a bigger air compessor would be better also run for a longer time.
12mm Plate will take ages to cut through, an oxy would be much quicker, but if your only doing 5mm and less it'll cut through it like butter.
Check out for what the prices will be on the inner and outer nozzle pieces are.
When it cuts out and won't work or cut you'll need to change the inner nozzle might get away with using the old outer nozzle otherwise you'll need to change it as well.
If it doesn't start arcing straight away when you turn it on there might not be enough air.
There's an auto cut off when you un-screw the nozzle cap so you will have to turn it off and back on.
Plasma cutters seem to be all the same deal, they don't change much when your only dealing with the little ones.
Try to be nice with the gun other wise it can crack and give you little zaps etc.
Oh and always have the earth connected you'll be able to still cut without the earth but it'll be real slow and it won't cut through anything thicker than 2-3mm.
You'll also want clean no water in the air otherwise it'll come out the gun.
Also when your finshed cutting air will still come out this is normal, to cool down the gun you should be able to stop this though by pressing the trigger once, wheather that's a good thing I don't know
When changing the nozzles there's ceramic air defuseser what ever you do don't let this crack or break they cost a fair bit you should get a spare with the machine if not just let the air stop then change the gun other wise the air can throw it out the gun.
Just some tips, I've used a couple of these for years, everyday. They are generally faultless, there's not much you could stuff up really.
They are handy nice clean cuts, just won't cut everything.
