Go to the settings, select your target device.
Go to the export tab, select the “add new song”, browse your mono wav files on the left window, then drag and drop your mono files to the right window to the corresponding channels.
(Set your mixer parameters in the top right corner icon.)
Add song name for your project than click on the “save and close” button
Now you can select the song in the left window, and select your USB storage device in the right window, than click on the export button.

Manual method:
Create a Recording folder on your HDD, create YOURSONGNAME subfolder, then put your wav files here, for the channel routing you have to use numbering prefix in the name of the files. Like this: 01_kick.wav, 02_snare.wav, 03_hh.wav)
Please make note the Folder name Recording without “s”