Hello, and welcome.
Yes, you're correct that you will do your first increases on row 3 and then every 4th row after that. So you will keep doing increases on rows 3 and 7 (of the 8 row pattern) until you have the correct number of stitches.
Oh by the way, I like your signature.
An English Knitter (nationality and method).
Feel free to call me either Clutter or Julie (my real name).
FO: Downton Hat
A sweater of a thousand yards begins with a single stitch. Lao-tzu's Granny