When I first started doing cables I always felt so AWKWARD trying to juggle both knitting needles AND a cable needle when it came time to knit directly from the cable needle. To me it looked like I was holding a porcupine with all those needle tips flailing around!
So at first I just slipped the stitches that were on the cable needle back onto the left hand needle and then knit them from there rather than trying to juggle the cable needle with the left hand one.
The only thing to watch for is make sure you haven’t twisted those slipped stitches around when you slip them back onto the left hand needle. They should go onto the needle in the same order they came off it when you first slipped them.
Although I usually knit directly from the cable needle now, I did much better in learning when I slipped the stitches back onto that left hand needle. And it was such a thrill seeing that little twist form and knowing that it would be very visible in a few rows!
Hope you do well and have fun!