K3tog is a double decrease, meaning you remove 2 stitches from your stitches count on your needles. It leans toward the right.
It consists to knit together 3 stitches.
Work according to pattern until you need to make a K3tog decrease.
Pass the tip of the right needle into the 3 first stitches from the left needle, going from left to right.
Pass the working yarn arount the tip of the right needle and pull the new stitche from the 3 stitches.