Leave the brackets there, slide the motherboard through the holes, you may have to bend them alittle.
The CMOS jumper pins  normal operation should be the set of pins away from the PCI slots.
Do you have your CPU plugged into the motherboard fan 1.
There are 2 rows of pins that the supply leads hook up to.
PN1 & PN2
PN1 is the one located closest to your ram slots, it's the second one in: from the edge of the board.
PN2 is the set of pins closest to the edge of the motherboard
PN1 and PN2 pin count starts from the edge of the board going in toward the PCI slots. So the pin closest to the edge of the board is pin1,then pin2,pin3 etc.
PN1 connections:
The Power led goes on pin 1,2 and 3 on PN1, the colored wiore is the hot side and goes on pin 1
The  Hard Drive led goes on pin 6 and 7  on PN1 with the colored wire going on pin 6
The Power on switch goes on pins 8 and 9 0n PN1 .
Thats it for PN1
PN2 connections.
The Reset switch goes to pin 1 and 2 on PN2 , pin one is closest to the edge of the board.
Speaker goes to pin 4,5,6 and 7 on PN2 with the colored wire going on pin 4
Now check your  Ram, is it inserted
Check video card, seated all the way in.
Check your cable to hard drive, pin 1  or the Red or black stripe on the end of the cable goin to your hard drive goes closest to the Red wire on the power feed Plug. The end going into the motherboard ,the red stripe goes to pin 1 on the Eide slot, Pin 1 is from left to right looking at the ram slots above for oreintation.
Make sure your ATX cable is firmly ilocked in place
Check and make sure no standoffs are touching the botherboard that aren't screwed in.
Carefully slide the motherboard into the slots at the rear, leave the clips on the USB and Ps2 holes , you may have to push alittle to get it in.
Power it up.
Good luck