So a few things:
1. Make sure you install the latest TuneECU software .apk direct from their website, don't stick with whatever old version you may already have had installed
2. I am assuming you have a decent BT OBDII device if you've flashed other bikes. The OBDLink LX, MX, MX+ ones are what TuneECU recommend. I used the MX+ with no issues.
3. I think you want the "All Markets Rocket GT No Restrictions 31012Map.hex" as you have the GT ("Triple Black" in your sig rather than "Black" for the R) right? I ask as you say R a few times above. They use a slightly different map, 31012Map vs 31018Map. It's in a zip file, but to test it I just downloaded it straight to my phone, extracted it with the Android files app, and opened it in TuneECU (v5.5.24) and it read it straight away. So my phone has successfully opened the 31018Map I used on my R, and just now the 31012Map that is used on a GT.
For loading:
4. Make sure you have a battery charger attached so the voltage doesn't go too low and the ECU shut off halfway. It takes 10-15 minutes to load the map which will give the battery grief. They say to pull the headlight fuse, but that doesn't kill the LED DRL's, so switch them off manually.
5. After the load, do NOT use the "reset adaptions" routine as it resets the crank position sensor throwing a code, and you need to then run the calibration procedure (I describe it in another post here).
6. Ride and enjoy!
If the previous poster wanting to know how hard it is is interested, my walkthrough of it (including my reset adaptions cock-up) is on my channel: