Depending on your Revit version and workflow, you can obtain libraries through several official channels: Autodesk Revit Content

Do not edit the original Autodesk library folder. Instead, create a Network Shared Library . Map Revit’s settings (Settings > Options > File Locations) to look at your server first, and the Autodesk library second.

Most users drag a family from the Autodesk library and hope it works. Power users rehabilitate them.