1. Click on the “Smart Controls” button in the upper left corner of the GarageBand window. This opens up the “Smart Controls” window at the bottom of the GarageBand window.
2. Click on the "Plug-ins" drop-down arrow in the Smart Controls window. Then click and hold on a plug-in slot to open the plug-ins menu.
3. Move your mouse cursor to the bottom of the list and hover over “Audio Units.” This will reveal additional menus of plug-ins organized by manufacturer. Select your Antares plug-in from the list.