The best place to install your Helium Mobile Hotspot would be a location where you expect the most density of people and foot traffic. Keep in mind that obstructions such as walls can absorb and reflect the signal in various ways. So it is important to ensure that the location you are targeting has a clear and unobstructed line of sight to where people will be utilizing it.
Also, note that installing your Helium Mobile Hotspot as high up as possible significantly increases the range and reduces the potential for obstructions.