Learn how to Upgrade Workshared Revit Projects with these steps listed in the link below.

https://knowledge.autodesk.com/support/revit-products/learn-explore/caas/CloudHelp/cloudhelp/2018/ENU/Revit-Collaborate/files/GUID-3A96685A-13B4-4ED0-9160-C84E95650370-htm.html?v=2018