The badges are Espruino Pixl.js boards, and come preprogrammed to do nothing more than display your name and a slowly moving cityscape.
However they feature a pretty full JavaScript interpreter that can run whatever JS you want, and can even interact with other Bluetooth devices.
Simply power off your badge by removing the battery and power it back on with a button on the right-hand side held down. This will make it connectable so you can program it (until it is restarted again).
Then just follow the normal Pixl.js instructions to get connected and start writing code. There are a bunch of tutorials
Once connected, type reset() - this'll remove any of the badge
code from RAM so you can play with a 'fresh' badge, without the old
code getting in the way.
If you want your old code back, just type load() and the old
badge contents will return. The same happens if you power cycle.
**Don't type save() or use the save on send option in the IDE
unless you want to remove badge code. If you blow it away you can
always follow the instructions in the next heading.
The standard badge code is here
Click this link on a Web Bluetooth capable device (Android, Mac OS, or Windows 10 with Chrome Canary).
Then follow the instructions you see on the right-hand side of the page.