Oh sorry, I wasn't very clear.
Press print screen.
Then open up Paint processor or something and paste.
Up pops a replica of your screen.

Where do i press this? Print screen? Sorry, I dont quite understand.

It's a button at the top of your keyboard, it says "Print Scrn SysRq", or at least mine does. Some computers (including my sister's laptop) require pressing a button next to the left side Ctrl key before it works.

It's part of the trio of least-used buttons on the keyboard.
PrintScrn
NumLk
and
Pause(who knows what this does? I do.)

mine doesn't seem to work, i even press that fn key next to control to do it.

Try pressing the shift key with the PRTSC key. That's what I have to do when I want to take a screencap from Rome: Total War.

Then I open up Paint, go to edit, then hit paste.

That worked! Thank you!

Now, how do i make my pics, well, bigger? The thumbnails of my screencaps are significantly smaller than gun images taken off the site.

GIMP should work.

GIMP? Sorry, dont know what that is.