Casting on additional stitches

The pattern says "Switch to main color, CO 6 sts at beginning of row, knit across established sts and backwards loop CO 42 more sts (72 sts total)"
I already know how to cast on the stitches, but my problem is that whenever I try to switch colors there is a gap between the stitches. Is there a certain way I need to join the main color with the contrast color? I can’t figure out what I’m doing wrong.

the trick in any color change is to wrap the yarns around one another. Check videos for “Intarsia” - that is work with color changes so most the videos show this twist.

Thank you! That really helped :heart: