The 24 pin ATX connector from the power supply plugs into the big black port on the motherboard.
The 4/8 pin CPU header from the PSU plugs into the 4 pin port at the top of your motherboard (If you have an 8 pin connector that says "CPU" on it, it should separate into 2 to make 2 4 pin ones).
All the small connectors from the front of the case will plug into the multicoloured port at the bottom of the motherboard, and each color represents a different connector from the front panel.
The white port with 4 pins right next to the front IO headers and the one at the top of the motherboard next to the RAM slots are fan headers for one case fan and a CPU fan. The CPU fan header is the one at the top.
The 2 white and 1 black ports on the bottom right are SATA ports for your HDDs and SSDs - one color should be SATA 3 and one SATA 2, if I'm not mistaken, so if you are using an SSD test booting from both port colors to see which one is faster. If you are using HDDs this is not a problem.
The yellow port on the bottom left is the HD audio port, this is where the front HD Audio labeled connector plugs in. The AC 97 connector that may also be there is not used.
The 2 black ports between the 24 pin port and the SATA ports are where your front USB connectors plug in.
Apparently, some people have had problems with the PC not detecting a power sensor on start-up since power sensors are all on the X-51 case's internal PSU, and displaying a warning when booting so to get around this go into the BIOS and turn off error reporting.
Here is a diagram that shows where some of the ports:
Please not that some ports like the USB ports and the top fan header are not shown.
Also, since the 760t has 2 front USB 3.0 ports, this will cause a problem since your motherboard does not have any USB 3.0 headers. You'll need to get a converter like this:
http://www.amazon.com/Silverstone-Internal-19-Pin-Adapter-G11303050-RT/dp/B00B1RM5YU/ref=sr_1_5?s=pc&ie=UTF8&qid=1449674667&sr=1-5&keywords=usb+2+to+usb+3+converter
to get them to work, otherwise you won't be able to use the blue USB 3.0 ports on the front of your case. This converter plugs into one of the black USB ports between the 24 pin port and the SATA ports. Then you'll be able to plug in the USB 3.0 connector from your case to get all of the front ports to work. However, keep in mind that even the blue USB 3.0 ports will function at slower USB 2.0 speeds.
EDIT: Here is a color code for the front IO connectors:
Keep in mind though that they may be different for your motherboard. Trial and error is the only way to get them to work if the colors are different.