If they hatch late the temperature needs to be raised. You can check your thermometer this way. Keep notes on everything you do during the incubation period. As you learn you'll have these notes to look back on. They will be the most valuable tool that you can have.
Humidity is checked by way of a hygrometer, or wet-bulb thermometer.
A hygrometer is simply a thermometer with a piece of wick attached to the bulb. Getting your humidity to become as accurate as your temperature is nearly impossible. It is almost completely impossible with a small incubator. Try to get your humidity as close as you can, and you'll be fine. Just being aware that humidity is important, and trying to get the numbers to come in close will be a huge help to your hatch.