You may find the ups comes with some cables to get you going. From memory they usually come with a c13-c14 cable which you are supposed to use to connect the pc to the ups... You then use the redundant cable that you used for pc to mains to power the ups.
For low power peripherals like switches, routers, WAPS etc that have power bricks or adaptors, I buy a four way extension and a wirable C14 plug - then cut off the mains plug from the four way and wire in the c14. I then plug this into the rear of the Ups and then plug the peripherals into the four way.