I'm not sure what they mean about running the cnc with a pc. Generally, we refer to posting or creating a program with a pc then down loading it into the cnc. To do this you would need a CAD/CAM softwear program on the pc. The CAD part of the program is used to do a drawing of the part either in 2D or 3D and the CAM is used to make a program that the cnc machine understands.
these CADCAM packages cost around $1200 and up to $50K. One example of a lower priced decent program is EZCAM. I have an old version of this and use it for 80% of my programming. The balance and more complex programming I do with Alibre and Visual mill 3 and 4 axis work. there are lots of different programs out there. Some work quite well at a low price for some people and some not so well. Almost all will give you a free test version to play with. A word of warning...don't just play with it and think you can make it work well for you. Make it really work before you buy. Read all the post here you can find about the programs and understanding you will hear both the bad and good about each. Make it work for you and if it will not, send it back.
You can also hand input G-code into the cnc and they do have some methods of helping to input a program code by hand on the machine.