Just download the latest build from the updates tab (build 79 right now). Drag and drop the zip into the content manager window (Need full version of CM), click on the three stripes next to the 'about' tab when it turns green and press install.
Go to content>mods tab and activate it if necessary.
Grab
Assetto4Seasons and/or
AssettoByNight
The dynamic lights mod will put an 'Extension' folder in your main AC directory. Go to extension>config>smart mirror.ini to change mirror settings.
EXAMPLE:
[REAL_MIRRORS]
ENABLED=1
SHOW_CAR=1
VR_STEREO=1
VR_LOCK=0
SHOW_HEAD=1
RENDER_PER_FRAME=0 ; set it to 1 to make real mirrors refresh less frequent, but have practically zero FPS cost
RENDER_ONLY_VISIBLE=0 ; doesn’t work with virtual mirror at the moment
You can also adjust the angle and FOV of your mirrors using an app. Just activate it in your app list after installing the mod.
None of these changes are permanent and it can be deactivated easily.