Atrium.onload()
Atrium.onload() is a function the user may define to run once after the Atrium page is rendered for the first time.
The function should be defined in a javascript file located in /YourInstanceName/userdata/extension/atrium/.
Example
If your instance name is "profoundui", create a new file on your IFS: /profoundui/userdata/extension/atrium/settings.js
Define the function like shown in the following example.
Atrium.onload = function() {
console.log("The Atrium UI was just drawn.");
}