Help understanding pattern instructions

Hello,
I am knitting a vest for my husband but do not understand the increase instructions. For the back of the vest I am instructed to work in the chart pattern increasing 1 stich each side ( working increases into the pattern) on the 13th row and then on the 12th row 5 times. Also what type of increase do I need to use. The pattern is for straight needles row 1 * knit, knit, purl, knit* knit and row 2 purl * knit, knit, knit, purl* I am beginning with 97 stitches on my needles that have been worked into two inches of ribbing for the bottom band.
Thank you so much,
Allison

When you’re instructed to increase in pattern, you need to expand your current pattern. So if you have. . .

knit, knit, purl, knit* knit and row 2 purl * knit, knit, knit, purl*

kkpkkkpkkkpk

you would increase it to

kkkpkkkpkkkpkk and then to

pkkkpkkkpkkkpkkk

See what I mean?

What I usually do on this type of increase is to either work a kp into the edge stitches or a pk, depending on what needs to come next.

However, since the back is purled all the way, you could do the increases on the back and then work the front in pattern.

I hope this all makes sense.