The DPN video that Amy did shows you what to do, I think. First, you will take one dpn and slip 25% of your stitches to it, purl-wise (this dpn will have the cast-on tail on it). Then, you will let that dpn dangle while you take the next dpn and slip 25% of stitches to it, purl-wise.
Then you’ll arrange the needles so that you’re holding the needle with the cast-on tail in your right hand, the connecting needle is at the bottom of the triangle, and the other needle is in your left hand.
Then you’ll start knitting with the empty needle… you’ll use the stitches in your left hand to knit with, just like normal, but you’ll use the cast-on tail and yarn on the righthand needle to work the stitch with. The empty needle is the one that you will knit on to.
The video explains it much better than I can :oops: but hopefully that at least gives you an idea?