First thing, tomorrow morning, go to your LBS and buy a floor pump. Look for models that have a built-in pressure gauge - these make it super-easy (and kinda fun, actually!) to pump up your tires before every ride. I have two - I keep one in my car, so if I'm driving to a ride I can pump up before we start.

Look at the max PSI listed on the sidewalls of your tires. Basically, they should be pretty hard. At about 100 psi, mine have just a teensy bit of give if I push hard on them.