Hi Anna T, winr here.
I always test my mobo's out on a big static bag before putting in case now.
I had a case with built in stands that were a little too wide and shorted on the mobo.
Unhook your power supply from the mobo.
put a jumper wire in the green wire socket and any black wire socket and turn on or plug in power supply.
Your power supply should be on now and fan should run.
If you have voltage meter you could check the voltage.
Burning smell usually means something fried.
This may sound silly but you could smell each component and see if one smells really strong on burning.
PIN SIGNAL PIN SIGNAL
1 3.3V 11 3.3V
2 3.3V 12 -12V
3 GND 13 GND
4 5V 14 PS_ON
5 GND 15 GND
6 5V 16 GND
7 GND 17 GND
8 PW_OK 18 -5V
9 5V_SB 19 5V
10 12V 20 5V