You can make 2 stitches from one stitch by knitting through the front and back of the stitch on the left needle (=kfb). This increase create a small line at the base of the new stitch.
Knit as indicated in the pattern until you have to work a kfb.
Knit the next stitch on the left through the front leg of the stitch, without letting it drop from the left needle.
Pass the tip of the right needle under the back leg of the stitch on the left needle and knit.
Let the stitch drop from left needle. you have worked 2 stitches in one.
You can recognise the new stitch created thanks to the line at its base.