Welcome to HBT!
Lots of folks have forgotten to add water to the airlock but your beer will be fine. It's very hard to mess up beer!
I like to leave my beers in the primary longer than most. Since this is your first batch, it will be harder for you because of new brewer impatience.
Let your beer sit for at least 10 days to a week then take a hydrometer reading. Are you planning on moving it to secondary? If so, after it has reached its final gravity, it's ready to transfer. If you are using primary only, leave it three weeks and bottle that baby up.