boot.dol or boot.elf are the names used by all homebrew.
The loader's filename is "boot.dol", the forwarder's filename is "boot.dol" too.
Priiloader can install one homebrew at a time into the Wii (not on SD or USB), and auto-launch it on boot.
What you need to do is tell priiloader which "boot.dol" to install.
You can install the loader's boot.dol but you will miss some features (like Devolution), or you can install the Forwarder's boot.dol (recommended, easier to update the loader by replacing only the file on your SD card).
The forwarder's executable is located in the AllInOnePackage3.0/Wad/forwarderDol/
rename the ForwarderV5.1.dol to boot.dol and place it on the root of your SD card, then you can install it in priiloader's boot menu.
As it's a forwarder, you need to have the actual Loader's executable on SD or USB/apps/usbloader_gx/boot.dol