Understanding Pattern

I am in the process of knitting a dog sweater, I am not sure I understand the following direction within the pattern.
‘Change to larger needles and work in St st for 2 rows. Working in St st, inc 1 st each side every row 9 times to 102 sts.’ I don’t know if it means to increase in the purl rows or just knit rows. If required to increase in purl row, how do you increase in a purl row?

Thank you

You’re going to increase on both knit and purl rows. There will probably be 2 increases per row, one at the beginning of the row and one at the end of the row.

You can do a purl front and back (pfb) but work these increases a little loosely so that you can continue to place them on each row.

Thank you.