Bixby is built into the OneUI, so it's already on your phone. You just have to activate it. Open your phone settings, go to advanced features and tap on Bixby to set it up. You can then go to side button and set it to activate Bixby on the long press. If you don't want to use the side button to activate Bixby, you can create a routine to use another button action to activate Bixby, but this requires Good Lock and the Routines+ module. I believe Bixby will still activate by voice either way. Not sure, because I don't use it.
