Magma app lives completely in a browser — which means that everyone can access it easily from their computers. There are two ways to start a new canvas:
Open link https://magma.com/ in your browser - you will be redirected to a new, unique address:
Alternatively, if you want to specify details like canvas size, click File → New and specify image details:
When prompted, please remember to sign in (or create an account if you don't have one yet) — this will automatically make you an administrator of any canvas which you create, which is very useful for moderating drawing sessions.