I understand the basic idea of cabling but I am not following a specific pattern. I have 46 stitches on my needle and want a large cable twist in the middle. so how many stitches do I need to knit purl and knit and how many go on the cable needle?

Half the sts you want total in the cable will be put on the needle. Take your 46 sts and you may want about 3 sts each side in garter st so the edges don’t roll. That leaves 40 and if you want 5 sts each side in purl (reverse stockinette stitch) you have 30 left. So you’d do the cable row as k3, p5, put 15 sts on the cable needle, k15 from the L needle, knit the 15 held sts, p5, k3. For a cable with that many sts you want a really really loose gauge, so go up about 3 sizes for the needle. Do this only about every15- 20 rows or so.

On RS rows where you don’t cross the sts you k3, p5, k30, p5, k3 and on the WS rows knit the edge sts at the beg and end of the rows, and the rest will be worked however they look. Knit the ones that look like knit sts and purl the ones that look like purls. Knit about 6 rows of garter stitch, then 10-12 rows of the knit/purl sts before you do a cable cross row.

Experiment a little, really wide cables like this are unusual and may not give you the results you want. You may want to do a couplethree smaller ones. Here’s a sitewith lots of cable patterns.