To change display units, you'll just need to tap the settings button in the top left corner of the main device list screen in the SensorPush app. On the next screen, under the heading "Configuration" you'll see switches to change units for the various measurement types.
Available measurement units include:
Temperature (also Dewpoint): Celsius (°C) / Fahrenheit (°F)
Barometric Pressure: Millibars (mb) / Inches of Mercury (in/inhg)
Distance: Meters (m) / Feet (ft)
These measurements only have one available unit and do not have a switch:
Relative Humidity: Percent (%)
VPD: Kilopascals (kpa)