Hi and welcome to Knitting Help!
OK, it seems to me that you've stopped after finishing a WS row. You would have 2 more rows and the row after that would be the cable cross row, a RS row. Yes, that would be the row to do the next k2tog. Continue with the k2tog every 4th row which will be easy to remember because it the same row as the cable cross.
I'm not sure which k1 you mean but you don't want to use any of the 6sts that make up the cable for the k2tog.
I think the cable pattern should be:
Row 1: P1, sl 2 on spare pin, K2, K2 from spare needle, P1
Row 2: K1, P4, K1
Row 3: P1, K4, P1
Row 4: As Row 2