When you look up into the night sky, you see only some of the stars on the celestial globe.
Some are on the other side of Earth from you, beneath your celestial horizon.
To orient, or line up, your stargazing position in reference to the celestial globe, you have to imagine where your celestial horizon and zenith appear on the globe.
In the Northern Hemisphere, locate the northern celestial pole by looking into the sky above the northern point of your horizon the same number of degrees as your latitude on Earth.
If you are stargazing at 40° north, at Philadelphia, Pennsylvania, for example, look up along your celestial meridian 40° from the northern point of your celestial horizon.
There you will find the North Star (Polaris) marking the celestial north pole. If you look 90° along your celestial meridian from the North Star, past your zenith, you will locate the celestial equator.
Your zenith will be at the declination that has the same number as your latitude, or 40° in our example.
Armed with all this information, you can find your own piece of night sky on the celestial globe.
The method in the southern half of Earth is the same, but there is no polestar that marks the south celestial pole.