To put in a lifeline, thread some smooth, thin yarn on a tapestry needle. Dental floss even works. Slide it through all the stitches that are on your needle. It works well and easily to put it through the little V at the bottom of the loop. Leave it in there as you knit and it will be there if you need to frog.
Just make sure you remember at which row you put it in so you know where to restart.
You can put it in at each repeat, or before a row that you find particularly difficult, and take it out after the next lifeline is put in.