Source: Afterdawn Forum
User: pryme_H

HOW TO INSTALL A FILE TO AUTO-BOOT

1. First off, what you need to do is to acquire whatever DOL file you want for auto-booting e.g. USB Loader Gx, USB Loader, CFG, uLoader et al. You DO NOT need to rename the DOL file. However, for easy identification you can affix the appropriate name. For example, boot.dol file for USB Loader Gx can be renamed to USB Loader Gx.dol.

2. Next, put the DOL file on the root of the SD card.

3. Now, run Priiloader again by holding the Reset button.

4. With the Wiimote scroll down to Load/Install option.
Press A. You should see the DOL file in there. Make sure it is selected, then press A once more. The file should install in a few seconds. Press B to return to Main Menu.

5. Finally, go to Settings. Change Autoboot to File. Subsequently, change Return to: to Priiloader or System Menu. The choice is yours. Make sure you save these settings. Restart the Wii to see if the applied changes took effect.