As an instructor there are three places from which you can access your Canvas Studio (formerly Arc) account; Global Navigation Menu, Canvas Studio (from the course navigation menu), and the Rich Content Editor toolbar found in course content.
Global Navigation Menu
In Canvas the Global Navigation Menu includes an Canvas Studio link. This link gives you direct access to your Canvas Studio account from anywhere in Canvas.
Arc Media Library
Instructors can view their Canvas Studio course collection through the Studio link in the Course Navigation Menu. Like the other tools on the course menu instructors can add/remove it by going to the Navigation tab from the course Settings page.
Rich Content Editor Toolbar
The Rich Content Editor is part of multiple features in Canvas including Assignments, Discussions, and Pages. To access Canvas Studio simply click on the Canvas Studio icon from the toolbar (as seen above).