Assuming you have an Android phone, open the Play store and search for TuneEcu. Pay, download, and install.
TuneECU - Android Apps on Google Play
Save the tune you want to load to your phone.
Ensure your Rocket battery is fully charged or on a battery tender. Remove the fuse for the headlights (optional), should be under one of the side panels.
Connect the cable from your phone to your Rocket (interface cable plug located between battery and rear fender). I used the Lonelec cable and it worked first time no problem.
Diagnostic Interface for TuneECU Motorbikes
Once you're connected to the Rocket, backup the existing tune to your phone, then load the new tune you want.
Disconnect, turn the Rocket off then on, then wait 12 minutes with zero throttle input (optional), reset once more then you're good to go.