Both sensors, the Bosch BMP180 for measuring the air pressure, as well as the DHT11 for measuring the air temperature and the relative humidity, need some libraries to get data out of them. These libraries can be installed easily using the IDE, which provides some very convenient functions to include libraries into the development system. The recommended way to do this, is to go along this path: Sketch ==> Include Library ==> Manage Libraries ==> Library Manager ==> "All" "All" Then, when you found the pacakge you need, just install it