First you have to Update your SteamVR and your Software on your Oculus headset
 Go and install ALVR and SideQuest Downloads are below.
 Setup SideQuest and Sideload the APK from ALVR  After Sideloading the ALVR software onto the Headset, go to your games and go to 'Unknown Source' and open ALVR
[4.1] If the ALVR software for pc werent installed, install it from the same Github.
[4.2] If the ALVR software doesnt automaticly start, Open it yourself and if it doesnt automaticly add your headset to the list, well you have to add it yourself.
 Then it Should boot into SteamVR
Files you need:
The current Version of ALVR, for me its v18.2.3
as of the current version I need to sideload 'alvr_client_oculus_quest.apk'
and the software that I need to Install is 'ALVR_Installer_v18.2.3.exe'
When Installing SideQuest I would recommend installing the 'Advanced Installer'
First go and google the Issue or look at the FAQ pages of the programs and if that doesnt help, slide me a DM and I will look if I know any fix. (I am by no means educated in Coding so I cant help you if it has program side problems you are probably better off Messaging the Offical ALVR or SideQuest support channels. But if its an error that isnt that Code sided I might be able to help)
Hope it helps!