I am a beginner and I just started knitting socks but I don't know how to connect the needles while casting on. Thank you!
If you are using 4 double pointed needles you would cast on 1/3 of the stitches onto one needle. Then hold a second needle right next to the first but sticking up about a third of the way. Cast 1/3 of the stitches onto the second needle. Do the same with the third needle. Now hold the 3 needles in a triangle and (using the fourth needle) knit the first cast on stitch off needle 1.
Some double points come in a pack of 5. In this case you would cast on 1/4 of the stitches onto 4 needles, form a square, and knit the first cast on stitch off of needle 1 with the fifth needle.
I found this video that may help you.