You actually got really good equipment, but there IS a bit more to it, to get it to work properly.
Sounds like your coil is loose in the ProTank, or there's juice in the air tube, or something - but you might kinda have to "start over"...
It might be best if you could get the dude at the shop to spend 10 minutes showing you how to fill and use it - any chance of that?
The voltage you want depends a little on the COIL - which is IN the ProTank (and you probably need a new one already - from heating it up without juice, or from hitting it with high voltage!). The coil is disposable - about $1.25 each, and they'll last a week or a month depending on if you got lucky, if you clean it, and what kind of juice you use. The coil is rated usually somewhere between 1.8 ohms and 2.5 ohms. That's ONE reason it's good to have variable voltage - to adjust for your particular coil. The other reasons are to adjust for your particular juice, and for your particular preference.
In general, you'll probably want to start at maybe 3.5 volts, then turn it up, and up a little more, until you think it's too high (any burnt taste is definitely too high) then go back one. That simple. MOST likely, you'll be in the 3.7 to 4.4 range...
So - the trouble is with your ProTank.
#1) Start with a new coil. Hopefully you have extras? Screw it in nice and tight.

#2) Refill the ProTank -
a) DO NOT get any juice down the middle tube!
b) Actually watch a couple YouTube videos on "how to refill a ProTank" first
#3) Start at maybe 3.6 volts or so, and work your way up...