Using the installation building symbols in 2020 Fusion is achieved by following these steps:
1. First, ensure to have the Universal Building Symbols catalogue installed (to learn how to search for and install catalogues, follow this link How to Check and Install Catalogue Updates in 2020 Fusion).
2. When in a design, select the icon shown below from the Catalogue Items palette.
3. Select the Universal Building Symbols catalogue from the drop down menu.