Ideviceinstaller- Need a proper guide for installation

Hi Guys,
The 1.4.0 dmg seems to be bugged & in order to overcome it we need to install the ideviceinstaller.
This installation is not intuitive (we saw a post how to install it is not informative enough),
Can someone be kind & post an easy guide end to end how to install it?
This will really help us in our automation which is stuck!