Since version 2.0, you can add games to WBFS partitions.
Before being able to open a WBFS partition, you have to install wwt and grant access to the partition. To open a WBFS partition, select “Open WBFS partition” from the File menu and choose your WBFS partition from the combo box.
Make sure you can see the game you want to transfer in the source window (which will usually represent a folder on your Mac). Once you’ve selected the game, you can drag it to the destination window which represents the WBFS partition. A panel will appear asking if you want to keep only the CHAN and DATA partitions: usually this option reduces the final size of the game, but if you are unsure, just leave it unchecked. When you click the OK button, the conversion will start and you can follow the progress by clicking the Conversions button on the right side of the toolbar.