You do not need to enable dual channel, that's automatic if you have the dimms in the correct slots. (see manual)
I can't really help you until you tell me if this is a AMD or Intel motherboard.
Please tell us what cpu and mobo your using and the exact make and model of the ram.
Most boards default to 1333, so that is normal, if it's an Intel system all you have to do is manually set the speed to 1600, and manually set the voltage and timings too according to the sticker on the ram.
If it's an AMD system, the only way to run 1600mhz is to overclock.
Asrock makes Extreme 3's with Intel and AMD chipsets.
I'm running intel i5 2500k on a the asrock extreme 3 gen3 mobo. also i'm using corsair vengence low profile 1600mhz ram 8gb that I put into the correct slots on the mobo. It said in the manual I could put the pair in either a1b1 or a2b2 I went with slots a2b2 to have more room away from my heatsink/fan.
You manual will tell you where to go to change memory settings. It can be tricky to find if you don't know what your doing. It should be set on "auto", you'll want to change that to manual.
You need to look at the sticker on your ram and then go in bios and manually set the speed (1600), timings (9-9-9-24 or something similiar) and voltage, (hopefully you bought 1.5v ram) according to what it says on that sticker.
So you'll set the ram from 1333 to 1600. Then you'll check that the voltage is correct (should be 1.5v, if not you bought the wrong ram). Then set the main timings. So if the sticker says 9-9-9-24, that's what you'll change it too.
Okay I found that it is definitely 1600mhz ram @ 1.5v and 9-9-9-24.
So now I just look at my mobo manual to see how to manually set the timing and just change it to 1600 and set the main timings to 9-9-9-24 and restart? Or is there something else I would need to do as well?