To increase the number of stitches on your row, you could make a yarn over, but that leaves a hole. To increase almost invisibly, a make one, abreviated M1, is a good choice. Book between two stitches you should see that there is a line of yarn between these stitches.
Step One: Knit to the point where the increases is needed.
Step Two: Insert the right needle into the line of yarn between the two stitches.
Step Three: wrap the yarn over the needle.
Step Four: Pull the yarn through the line.
Step Five: Continue knitting the rest of the row.
Here is the video, it shows me knitting one, then doing a M1, then knitting one, then a M1...