Actually, all audio files located in the music directory on the SD card and a folder with the same name on the internal storage of the phone will be automatically indexed into the WALKMAN app by the operating system. So just copy all your music files into one or both of those folders.
You can touch the WALKMAN icon in the top left hand corner of the WALKMAN Home screen (Next to the word Home) and select the songs option to see what the app has indexed for you.
There is even a shuffle option there at the top of the list too.
You can also use the file commander app (If it is installed on your device) in the main menu to explore your files, just navigate to the music folder. If you don't have a file manager app installed, just visit the play store and pick one up. There are loads and plenty of free ones.
If your files don't show up they are either encoded incorrectly and you just need to re-encode them and copy them over into the right place. Or you are trying to play an unsupported file type. In that case you can use a computer application to transcode your audio into a format which is supported.
I hope this info helps you enjoy your music collection using the WALKMAN app.
