Check if your ArchiCAD version is supported by Revizto. Revizto export plugins are Windows only, there is no plugin for ArchiCAD on Mac OS. You can find the list of all the supported versions here: List of Integrations with Authoring Tools
Make sure that you have installed Revizto after installing ArchiCAD. If you installed Revizto first, you may need to reinstall or repair it.
If everything above is correct but Revizto add-in doesn't appear in ArchiCAD you should do the following steps:
Go to “Options” -> “Add-on Manager”
Click on “Search for more Add-ons...” and select the folder where you have installed Revizto (by default it is “C:\Program Files\Vizerra LLC\Revizto4”). In that folder select *.apx file that corresponds to your ArchiCAD version, for example, "ReviztoExport19.apx".
Click OK twice, reload the project and you'll see the Revizto tab.
See also the ArchiCAD plugin video tutorial for the details on how to enable the plugin and how to work with it.