Put them in the right folder. Either download and install them yourself without an updater program, or change your settings in the Curse Client to point to the right folder. If you're on a Windows machine and installed WoW in the default location, that is:
C:\Program Files\World of Warcraft\Interface\AddOns
I believe the Curse Client only wants the bolded part, but addons themselves go in the AddOns subfolder.
If you don't know where you installed WoW, right-click on the shortcut you use to open the game and click the "Find Target" button. It will open the folder, and you can copy/paste the path out of Windows Explorer.