Hi, welcome to the community.
You can use the Fitbit Studio to create the code for your watch face. And then test it either using the simulator or your device.
You can now also create using the command line interface and then test the same way.
The fitbit studio link is http://studio.fitbit.com.
Might also be a good idea to read up the development guide https://dev.fitbit.com/build/guides/
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