seriously, you dont have near enough knowledge to do this if you just asked those two questions.
Not necessarily true. Not saying I think he SHOULD try rooting though. I mostly agree with what aplsucks said.
OP, if I were you, I would wait on rooting for a true One Click method. I hate to do the whole jump to conclusions thing, but judging by your op you might not have what it takes at this point.
That isn't to say you're dumb, or incapable though. Anyone can read up on how to do things and learn them. I just feel that I should warn you: right now, rooting is not an easy process for someone who doesn't have experience with cmd/adb.
My recommendation would be that you wait a while longer, unless you're willing to seriously learn what rooting entails. Just be patient either way you go with it, and do it correctly.
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Anyways, I will answer your thread title in the interest of helping out

When you plug your phone into your computer via USB, drop down the notification bar on your phone. Click the notification that says "Charge Only" and select the Hard Disk (or maybe it says "Disk Drive") option.
After that, let it sit for a few seconds to recognize the change, and then you can go into (it comes up in the J:\ drive for me, so I'll use that; it may differ for you):
My Computer > Removable Storage J:\
This will show all the files contained on your SD Card. If you want to move a file to it, simply find the file wherever it is on your computer, and drag and drop to your Removable Storage/SD Card.
After putting your phone into Hard Disk Mode, it's the same methodology as a USB Flash Drive, if you're familiar with those.