How to calculate what height the satellite should be in order to have such an orbit.?

The derivation and calculation is shown here: http://en.wikipedia.org/wiki/Geostationary_orbit#Derivation_of_geostationary_altitude

One way would be the height at which the acceleration of centrifugal or rather centripetal force ( A = V² / R ) equals that due to gravity ( A = G M₁ / R² ), this results in R = G M₁ / V². Note that the velocity is the circumference of the orbit multiplied by the rotations per second which of course is constrained by an orbit every day.

Mind you, geostationary communication satellites are not very good for two way communications as the distance is far enough to cause a serious latency, such satellites are expensive to launch and can not be repaired or upgraded once launched. The entire concept will likely be replaced by semi-automated high altitude UAV's or blimps. This will have the unfortunate effect of depressing the commercial space launch industry and may drive fledgling startups out of business. Geostationary satellites are old technology soon to be obsoleted.

The satellite should be more than 35000 kms in height above the earth to attain a geo-synchronous orbit and later with further thruster firing, the altitude is raised to between 36000 and 40000 kms. At such height, the satellite will attain a geo-stationary orbit above the equator, with 24 hours of orbital period, same as the earth's rotational period.

Calulater