Mic, Preamp, Noise, Help...

Hi I'm totally new to any real recording equipment so I have some very basic questions.

I have a mic plugged into the preamp then into my computer. As regards gain and output on the preamp: What?

If I put the gain down till the noise goes away (almost all the way down), I have to turn up the output pretty far to get a good vocal out. If I turn up the gain of course, the noise comes through.

Am I doing this right? Would it be 'legal' to have the gain way down and the output way up? Is that logical?

Do I need to be rid of all the noise?

True American are you there? Basically, what I want to know is how do I set this thing so the vocals come through without noise.

Any input from anyone would be greatly appreciated.