A simple rope cable knitting pattern:

Abbreviations:

k = Knit
p = Purl
C6b = (cable 6 back)- slip 3 stitches to a cable needle and hold at the back of the work, knit 3, then knit the 3 stitches from the cable needle.

Cast on 12

Row 1: p3, k6, p3
Row 2: k3, p6, k3 (do this for all alternate rows)
Row 3: p3, k6, p3
Row 5: p3, c6b, p3
Repeat above rows til desired length