Installing an omnidirectional antenna is easy. The rule is: mount the antenna as high as possible outside on the wall of the house but do not increase the cable length unnecessarily. Cables dampen the signal (depending on cable quality). With an omnidirectional antenna, the cable length should not exceed around 8m (low loss cable like LMR-195), otherwise all you gain with a good antenna would be lost.
Installing a directional antenna requires a bit more work. Again, mount the antenna as high as possible without excessively increasing cable length. With a high gain antenna like the Yagi Antenna or Wall Mount Antenna, cable lengths of as much as 15m are possible (providing usage of high quality, low‐loss cable). Then, the antenna needs to be aligned towards the nearest base station. If you use your LTE/3G adapter or mobile phone in order to measure signal strength, you must wait up to 60 seconds until your display shows you the correct measurement. Turn the antenna by increments of 10° degrees to find the direction of strongest signal. It may help to check with your provider where your nearest base station is located. An alternative is to use a mobile spectrum analyzer to help identify the direction of the strongest signal.