Repeats are a very hard workout. You take it one at a time (whatever distance it is you are doing) and you give it an all out effort as if you were just doing one. Then you do it again. And again. And again. Depending on how many repeats your workout calls for. I try to shoot for 6:30 miles when I do this...at least sub-7 if I can. Running this pace for a continuous 3 or 4 miles is REALLY hard for me. But the more I do repeat training at a fast pace, the more my body can adapt to running at a fast pace for longer distances.
Here is the workout:
4 x 1 mile repeats.
Try to keep your times as consistent as possible. Take it one mile at a time and recover between each one. Each mile should be an individual effort. Run them hard.
If you are a beginner you can do 2 x 1 mile repeats, or 3 x 1 mile repeats. Or you can do 5 x 1/2 mile repeats. Just make sure the focus is on an all out effort on each one with a recovery between so you can give it a good effort each time.
Run. Rest. Repeat.