how is einstein theory connected with GPS?

Einstein's theory of relativity is not related to GPS at all. The theory of relativity is a physical concept (e=mc^2). It dictates how energy and mass is related.

GPS uses the time signatures on satellites that the US govt put in orbit around the earth to triangulate the exact location on earth that the GPS device is located. It can be used for navigation such as on Garmin units, or can be used for tracking people or vehicles. An example of this can be found on www.wavecontrols.com. Check it out.

GPS involves satellites orbiting a massive body at different elevations, and a ground receiver on the surface of the massive body.

So for satellites, you have orbital speed that has one effect on its internal clock (more speed, fewer clock ticks), and position in a gravity well that has another effect (higher altitude, more clock ticks).

And down here on the surface, we just have the position in the gravity well to figure on, since we are moving very slowly.