To access a Unity Project on which Collaborate is enabled, you must be added to the Organization under which the project was created. If you are already a member of the organization, then verify that you are a Manager for that Organisation.
1. Open Unity Hub on your machine and select the project tab. You should see a grayed-out project with a cloud icon.
Then click on the cloud of the project that you want to download.
2. You will then need to select or create an empty folder. Unity will download and place the current version of the project inside. Once this is done, the Editor will open the project and you will be able to start developing.