You can select mission packs or mods in the "CLI" panel of the startup dialog.
Hold the "Option" key while starting the desired Quake application.
Go to the "CLI" settings panel.
Select the + button and select either "-hypnotic" or "-rogue" in the pop up menu.
Press the OK button.
Hold the "Option" key while starting the desired Quake application.
Go to the "CLI" settings panel.
Select the + button.
Select the "-game" option in the pop up menu.
Enter the name of the mod in the text field.
Press the OK button.