Making my 1st buid

Well first off, what case did you buy? You can check the manufacturer's site; they usually provide some info.

But looking at my PC, for an ATX mobo...
- one near the I/O shield (top left)
- one basically at the top-middle (above the CPU socket)
- one at the top-right coner (basically the edge)
- one below the audio ports (near the first PCI-E / PCI slot)
- one under the CPU socket & below the RAm slots
- one right of the RAM slots, where the 24-pin power cable is
- one at the bottom-left coner
- one under the SB...where the USB headers are
- one at the bottom-right corner...near to where the front panel connectors go

Another thing you can do is just place your motherboard onto your case, line it up, and see where all the screw holes are.