To use the gauges, then simply : 

1-Download the Gauge Anthology 1.5 Asset Folder .zip

2-Unzip it onto your hard drive

3-Register it as an asset folder : in the Edit / Preferences / Asset Librairies, click the + button and paste the adress of the unzipped folder

You're done and can add the gauges onto your model

Regarding the Dial Generator :

Arc radius : from 0 to 360°. For instance if you want a dial that had a half disk shape, type 180
Arc Width : as it says will determine the width of the lines (arcs and principal iterations). sub-iterations shall be half of the arc width
Switch 1 will enable principal exterior iterations
Grad 1 nb : number of principal exterior iterations
Grad 1 lgth : length of the principal exterior iterations
Switch 2 will enable principal exterior sub-iterations
Grad 2 lgth : length of the exterior sub-iterations
Switch 3 will enable principal interior iterations
Grad 3 nb : number of principal interior iterations
Grad 1 lgth : length of the principal interior iterations
Switch 4 will enable principal interior sub-iterations
Grad 4 lgth : length of the internal sub-iterations