To install the two SSDs, you will need to remove two of the internal hard drive trays and screw the drives to the bottom mounting holes:
One end plugs to the drive, the other end will need to be plugged to an available SATA port on the motherboard.
Next step is to grab a SATA power cable from the power supply bag that came with the computer. You will want to look for a cable such as this one:
The 6pin end of the cable will need to be plug to the power supply.
Remove the following screws for the PSU shroud to gain access to the power supply:
You will want to plug the cable to one of these ports on the power supply:
For reference as well: