You can access and start installed and authorized add-ons directly from the application the add-on extends (Gmail, Docs, Sheets, Slides, or Forms).
Accessing Gmail add-ons
Gmail add-ons that you have installed automatically appear in the Gmail
user interface when you open or compose a message (depending on which interfaces
the add-on provides). Gmail represents each add-on by a
small icon, as specified by the
logoUrl field in the add-on's
Clicking an add-on icon opens the add-on interface, and clicking the icon again hides the interface. The location of the icon depends on whether
For Gmail add-ons that extend the message UI, the add-on icons appear in a vertical column to the right of the open email thread, under the menu. The name of the add-on appears if you hover over its icon.
For Gmail add-ons that extend the compose UI with compose actions, the add-on icons appear in the horizontal row at the bottom of the compose window. The add-on icons are placed to the right of the standard icons for message formatting, attaching files, and so forth.
On mobile, the add-on icons appear as a horizontal row at the bottom of the currently open message or draft. Clicking an icon opens that interface at the bottom of the message.
For Gmail add-ons that extend the compose UI with compose actions, the add-on icons appear in the compose view's top-right menu.
Accessing editor add-ons
Most editor add-ons create one or more menu items in the Add-ons menu of the editor. It's a best practice to create at least one menu item for an editor add-on to serve as the initial launch point that explains the add-on's purpose and usage. Selecting one of the add-on menu items causes some functionality of that add-on to start; often add-ons use menu items to open the main sidebar or dialog that represents the primary add-on interface.
Google Forms doesn't use the same menu bar as the other editors. Instead, you can find Forms add-on menu items by clicking theicon in the upper left of the Forms editor interface. Forms add-ons only extend the form editor, not the forms that are sent out to for replies.