Second (checking part) execute the firmware by plugging the board into a computer. Be careful: It is important to use a computer with running operating system - just a power supply is NOT sufficient! If only LEDs "cycle" and/or nothing else happens within a minute or so, your board is revision two or older and you can continue.
Third (hardware part) change your boards layout (via soldering) by swapping connections PD6 and PD7.
Fourth (automatic part) execute previous (step one) installed firmware by plugging the patched board into a computer. (Again: A computer - NOT only a power supply!) The firmware will check if there is USB connectivity via the new PIN (PD7). If it is, it will modify the bootloader to operate via new PIN (PD7) as revision three from now on.
Soldering is required for the hardware part (step three). Of course the board needs to be switched off during the process.
Basically you first unsolder the cables end at PD7 for the PROGRAM button.
Then you disconnect the corresponding pin header from microcontrollers PIN (PD7).
(This ensures an important safety measure: The future USB (D-) line must not be accessable on the outside (i.e. on a breadboard)).
Now also disconnect PIN PD6 from its inner USB D- connection rail. Connect the MCUs PIN PD6 with its corresponding pin header.
Extend the inner USB D- rail and connect it to MCUs PD7. (Its pin header stays disconnected!)
Solder the cable to MCUs PD6, which already should be connected to its pin header.
Done! Now you need to continue with step four...
Finally you may want to install a revision 3 update to get recent bootloader.