The plugin is freely available in Adobe Exchange and compatible with Illustrator CC 2018 and CC 2019: https://www.adobeexchange.com/creativecloud.details.102730.html.
You can also get it from within Illustrator by clicking on Window in the menu bar and selecting Find Extensions on Exchange...
On the Adobe Exchange website, make sure that the Extensions tab is active and simply search for "canto connector".
Once the extension is installed you might have to restart Illustrator.
Go to Window > Extensions and activate Canto Connect.
Select the relevant Canto Environment from the dropdown list. For US customers, it's usually "canto.com" while the rest of the world usually has "canto.global".
Log in using the same Canto credentials you are using when logging in to Canto in your web browser.
Allow the plugin access to your Canto account.
The message will ask you to grant access to the Canto Photoshop Connector instead of the Illustrator one. Both Adobe applications share the same plugin which is why Photoshop will be displayed in Illustrator too. This step is correct though.
How to use the plugin
Note: The Canto Connector extension will not be visible on the Illustrator Dashboard, you need to create a new or open an existing file first.
Once a document is opened in Illustrator, your Canto Main Library is displayed within the extension, making it easy to work with images in Illustrator.
If you are looking for a specific image, simply enter your search term(s) into the search bar.
Alternatively, you can browse through your folders and albums.
Hovering over an image shows additional details.
While hovering and clicking on the little menu icon on the right, opens the detail view of an image from where you can open it in Illustrator or add it as a new layer.
The default behavior when clicking on an image can be changed under Configuration (2).
Furthermore, you can adjust the preview size to your liking (1) and filter what asset types you want to display within the Canto Connector extension (3).
All images you are currently working on in Illustrator are displayed under Assets. From there, you can upload them to Canto.
However, you cannot upload unsaved files to Canto. A message will notify you about this when attempting to do so.
First, save your work in Illustrator. You will notice that the icon changes to a green cloud with a strike-through effect. This indicates that the file has been saved but not yet been uploaded.
A modified image can only be uploaded as a new asset. Therefore, you will see the folder and album structure right away.
When uploading an unmodified image, you have the option to either save it as a New Version or as a New Asset.