(K1,yfwd,K1) in one stitch is an increase.
knit into the stitch, but don't slide it off the needle. Bring the yarn forward between the tips, and with the yarn still in front, knit the stitch again, then slide it off. You'll have 3 stitches where you had 1.
For the next instruction,
k1, (K1,yfwd,K1), k1 (another increase in the center stitch as above). You'll have 5 at this point.