I just want to give you the confidence to do this pattern! If you can purl and knit, and place a marker, (and have a circular needle and cable needle) then you can do this one! Have you watched Amy's videos on cables?
The pattern also describes how to the different cables as well.
One hint to make the pattern easier to understand is to copy and paste the whole pattern into a word processing program, like Word. Then use the "find and replace" feature to replace the abbreviaions with the whole words like "Rnd" becomes Round, p becomes purl, k becomes knit and so forth, pm becomes place marker.
But basically to sum it up, you will be knitting a large tube. You cast on 100 stitches onto your cable needle, carefully join into a circle, knit in K2P2 ribbing for 12 rows, then place a marker, knit a side panel pattern, place another marker, knit a main panel pattern, place another marker, knit another side panel pattern, place another marker, and then purl around until you get back to your first marker and do side, main, and side panels again, for 35 rows x 3, then 6 more, rib again for 12 rows, and bind off.
Then you make your strap. They have you knit it flat and then seam it but who really wants to seam for 48 inches? I'd try double-pointed needles for that and you'd have your tube already!