I grab them off eporner or spankbang (using the 'download them all' extension and the "allow right-click" extensions in firefox.) Then I turn on the Quest Link (either cabled or air link, my setup is fast enough for air link). Then I use an app called DeoVR to watch them.
You need the Occulus App for Windows and DeoVR for windows.
Alternatively, you can download DeoVR from the Meta Quest store, and download the VR files directly onto your occulus and watch them from there. But VR files are large, and you most likely only have the 128GB model. So that space goes quick.
There's a folder icon at the bottom of the DeoVR interface that lets you browse local files.
The Quest DeoVR app also works with SexLikeReal dot com (which you can type in the url bar at the top of the app) and you can view a few previews or free videos there.