The Canvas event has started. You can go there with the above link and sign in by entering your instance name (lemmy.zip if you're a user on this instance) and your username (no password entry is required).
After that you will receive a DM on Lemmy with a code that you can enter on the canvas site to confirm your identity. You might need to press 'Sign Up' afterwards on the main Canvas and it should show your username meaning you're good to go.
Quick rundown of the rules:
1 pixel per minute. Up to six stacked pixels. Notification and timer for upcoming pixels. No hateful/illegal/NSFL content is permitted.
Event runtime:
This event will last 72 hours, starting August 4th, 12:00AM EST (4:00AM UTC) and ending on August 6th, 11:59PM EST (3:59AM UTC)