Increase refers to the number of stitches in a row/round. This is usually achieved by crocheting multiple stitches into one spot. Sometimes you only need to increase by one or two stitches at a specific spot and other times you may be asked to increase by a number of stitches evenly on one row/round. If later is the case, divide the number of stitches in the previous row/round by the number of stitches you need to increase. That is the stitch number you will be increasing in. If you have 30 st and need to increase evenly by 5, you will crochet two stitches into every 6th stitch (30/5=6).