You can add sounds from your personal sound library by going to the user folder in the Drum Sound or Loop Browser and selecting the User section from the Pack filter, then pressing the Import icon. This will launch a browser that will allow you to choose sounds from any location on your device. See image guide below.
Step 1: Accessing the Drum or Loop Browsers
Access the Drum Sound Browser by tapping the Folder icon on an empty drum pad
Access the Loop Browser by tapping the Plus icon on an empty audio clip (on an audio track)
Or by double tapping in an empty area of an audio track in Timeline View
Step 2: Tap the Pack Filter Menu
Step 3: Tap the Pack Filter Menu and select User
Step 4: Tap the Import icon
NOTE: If you select "User" in other than the drum or loop browser (e.g., patch browser), the Import icon does not appear.