I've been reading

I've been reading all night to figure out how to use my external flashes that I have, and all that i could figure out is that you want to measure the light that you have in the room and then stop 2 down. Which does not mean just to move two stops down from like f/4 to f/5; but it means to divided or multiply depending which why that you are going by 2. So i end up with f/4 to f/8, and then you adjust your shudder speed to relate. If you just move the f stop to f/8 then you would keep the same shutter speed, lets say 1/60. But then if you want to adjust and say go with a faster shutter speeded 1/125 then you need to bring down the f stop to f/5.6 to adjust on the scale. So i understand that part but my question is on the stobest's blog they don't tell me what to put my flashes on. They say to put i on manual but when I have it on manual it just has a much of different numbers going from 1/128 to 1/1 and then on the side it has a +/- .3, .7, and I have no idea what that means because that side does not explain it. So if anyone has any tips or answers I would be very thankful.