There is a video here. It is under cast-on I believe. It is also called an invisible cast-on. There are a few different ways to do it.
I don't crochet so the easiest way for me is to use a crochet hook and pull the sts onto the needle with the hook and then go back and knit the first row, then go on with the pattern.
If you search for it on here in forums, several ppl have also posted links to other videos and other ways to do this cast-on.