There are two ways to increase in knitting, ‘make one’ and ‘yarn over’
How to ‘Make one’ in knitting
Knit to where the increase is to be made. Insert the tip of the LH needle under the running thread from back to front.
Knit this loop through the front to twist it.
If you are working M1 on a purl row, you purl the loop through the front.
How to Yarn Over in knitting
Between Knit Stitches: Start with yarn at back. Bring yarn forward from back to front between the needles and back over the RH needle.
Between purl sts: With the yarn at the front of the work, take it from front to back over the top of the RH needle, continue round, under RH needle, and hold to front ready to purl next st.
Between a knit and a purl st: Start with yarn at back. Bring yarn forward between the needles, take from front to back over the top of the RH needle, round RH needle and hold to front to purl next st.
Between a purl and a knit st: Start with yarn at back. Take yarn back over top of RH needle and then bring it between the two needles so that the yarn is not at the back of the work. Knit next st.