Very often, when a needle comes out of the package, it is curled up. Dipping it in very hot water is supposed to allow you to straighten it out. This doesn't happen with Addi Turbo needles, which is one of the reasons I like them so much.
As your knitting gets heavier, though, that helps control the curling, too.
To join, bring your stitches all around the needle with the working yarn in your right hand and the first cast on stitch at your left tip. Then start knitting. Make sure that your stitches are not twisted, though.
Here is video.