I think we have all been down this road.
Did I buy the right one, why isn't it working right. Should I have spent $800 on a reef octopus. Well don't fret your fine, skimming is actually a pretty simple concept and the one you have will be just fine.
Your looking to get bubbles that increase in size right around where your skimmer starts to taper off.
___.|::::| <-- no little wet bubbles up here only big bubbles or froth
__../OOO\
__./OOOO\ <-- were looking for bubbles to start getting bigger around here
__|o.o.o.o.|
__|::::::::| <-- lots of tiny bubbles yay.
You have a couple of controls to accomplish this
1. depth of the water - increases back pressure on the outlet of the skimmer thus reducing flow slightly and increasing the water level inside the chamber should be in the instrucitons if not start at 8" and go from there you want to make sure the the water level minus bubbles is below the taper.
2. the outlet valve of the skimmer. close to increase back pressure (flow down level up) open to decrease (flow up level down)
3. the air line supplying the needle wheel (assuming you have the needle wheel style skimmer) as most do. if your skimmer didn't come with one you might have one that is too narrow, or possibly you made the line too long. long and narrow = less flow = less bubbles = bad. it came with your skimmer and you don't have to mess with it, my first skimmer was el cheepo and I had to buy air line tubing myself and install it.
If you have large bubbles in the taper with out getting small wet bubbles at the top of the neck its working don't worry if you don't get thick brown skimmate it might mean your water is clean. if you check back in an hour or so you should see foam forming at the top of the large bubbles this will work its way up into the cup eventually.
Also yes run it 24/7/365 unless your adding something that says "do not run skimmer for x hours" which at this point you should probably get your skimmer running well first then mess with other stuff.