How to add a SSH key to a User for Authentication

1. Obtain your user's Public SSH Key from them (most common). Or, create a key and send it to them (rare).
2. On the main left menu, click Users
3. Select the user and click the Authentication tab.
4. Click the toggle on for Authentication via SSH Key and click Save.
5. Click the SSH tab then click the Add SSH key button.
6. Provide a name or unique identifier for the key in the SSH Key name field.
7. Paste the SSH key contents into the SSH Key section.
8. Click the Save button.

Now the client will be able to use that key to connect to the site without the need to use a password.