1. Navigate to System | Advanced.
2. Make sure SSHd Key Only is set to Public Key Only:

3. Navigate to System | User Manager. Click on the Users tab (it should be selected by default).
4. Click on the Edit icon (the pencil) for the admin account.
5. In the Keys section, paste the client's public RSA key (that can be the RSA key you created in the previous recipe). When pasted, the key should appear as a single line. Make sure your text editor does not insert any line feeds, or authentication may fail:

6. When done, click on the Save button.