DR3 mobile device: How to sideload an .apk file (using a memory card)

You will need a MicroSD memory card (minimum 2 GB, maximum 32 GB) and a built-in or external card reader on your PC.

On the PC, download and save your desired .apk file (either to the PC's drive, or directly to the MicroSD card).

If you saved the file to your PC, copy the file to the MicroSD card.

During this process, the device will power off and reboot. On the device, save any data if necessary. Open the battery compartment and remove the battery. The MicroSD card slot is on the right side of the battery compartment. There is a MicroSD illustration on the label inside the battery compartment showing the correct card orientation. Insert the MicroSD card and push until a click is felt/heard; the card should stay inserted.

Replace the battery and lid. Press and release the power button to start up the DR3.

Use the app File Manager. At the top, tap the memory card icon (blue rectangle with gold edge).
Tap your .apk file. Follow any prompts that might appear. After the process completes, run the app by tapping Open at the bottom.