This sounds like it starts with garter stitch, so it doesn’t much matter - whichever side you think looks better can be the RS. Once you’ve decided, mark the middle of the row with a safety pin or different color of yarn. ‘Facing’ you means the row you’re about to work on next. The row that isn’t marked will be the WS row then and you start the instructions for the WS row.
You can call that one the RS row. You decide because it’s a reversible pattern. Just mark it so later on you may have a stitch pattern that does have a RS or WS to it and you’ll be able to tell which is which.