The Revit client's Family Browser user interface is organized hierarchically.
The top level is the library, which can be either shared or not shared with selected users or user groups. Uploading families to this level will not make them visible in the Family Browser. Libraries consist of groups, and a single library can contain multiple groups.
Groups are located one level below libraries. They can contain subgroups and tabs, and multiple levels of groups are possible. Like libraries, uploading families to this level will not make them visible in the Family Browser.
Tabs are the next level down from groups, and this is typically where your families will be found. Tabs can also have subfolders, which are like nested tabs and contain families. They can be multiple levels deep.
To ensure that you can see your uploaded families in the Family Browser, you must organize your folder structure hierarchically in this manner. An example is as per image below.
In order to create this folder structure, you might need to create empty folders for Libraries and Groups and name them appropriately. After that, you can rearrange the folders by dragging and dropping them into their respective parent folders to achieve the desired folder structure.
First, make sure that the folder structure is correct. To do this, select the top level node and click on "Assign Folder" from the top toolbar. This will allow you to assign the folder as a library and choose which versions of Revit you want it to show in.
Once you have assigned the top-level folder, you can move on to assigning the remaining folders to the correct Groups, Tabs or Sub Folders. If you make a mistake, don't worry - you can easily reset the folder and unassign it or assign it as another level open.
After completing the assignments, navigate to the user manager to assign users who need access to the new library.