If it's a magazine for teaching it should have instructions in the magazine for different techniques.
It sounds like you are doing intarsia. You will have a length of yarns wrapped on a bobbin or just hanging (personal choice) so when you come to it it will be ready to use. The yarn isn't carried across the work, but picked up as you get to it. You twist the yarn so as not to create a hole.
I haven't done a lot of this, but here are some videos and instructions to help you out if you can't find them in the magazine.
Video here on KH..scroll down