No — there is no app store, theme installer or watchface gallery for the Artemis Watch 2.0, and nothing to download onto it in that sense. What you add to the watch, you build.
How adding things actually works. You code the watch through CircuitBlocks at code.circuitmess.com — your own watch faces, animations and simple apps. Two expectations to set straight:
Your program replaces the stock software until you restore it — it does not appear as an extra app alongside the built-in ones.
Your last program stays on the watch and starts again on its own after a power cycle. Only the last program you ran is kept, and your sketches stay saved in your CircuitBlocks account. The Restore firmware button brings back the standard watch whenever you want it. The detail is in What happens to my CircuitBlocks program when the device resets?.
Community projects exist — as code. Other owners share what they have built on the community forum and in our open-source repositories on GitHub, and you can study or adapt their work in your own CircuitBlocks sketches. See Is there a community forum where I can show off my projects? for where the community lives and What is "Open-Source" and why does it matter for my kit? for what being open source lets you do.
If you are new to it, Coding your Artemis Watch 2.0: where to start is the gentler on-ramp.