In this pattern, you will be making the washcloth as if it were a diamond. So you would start narrow, get wider, then taper back down. You need to be able to do increases and decreases to do this.
This is a good pattern to practice your increases/decreases because the pattern is small and you won't get too frustrated if things don't work out. And, you can always frog it and try again.!.!.!.!
If you want to just do a straight across square then just cast on the number of stitches required by your package gauge to get 6 inches and then just work rows back and forth till the work is also 6 inches long, then bind off.