To set up Single Sign On using Carousel and OneLogin you'll need to have administrator access in both systems and have two browser windows open. Then follow these steps and you'll be all set.
Log into Carousel in one browser window and navigate to Settings > Users > Single Sign On
Click the 'New Identity Provider' button.
Log into OneLogin in the other browser window and navigate to Administration -> Apps
Click 'Add App'.
Type "SAML test connector" in the search box. Select "SAML Test Connector (IdP w/attr)".
Type a friendly name, click Save.
Use this information from the Carousel window...
...to fill in this information in OneLogin.
Ensure the SAML fields include Email (attribute and NameID). First Name and Last Name are optional.
Change the SAML Signature Algorithm to SHA-256. Use the information found on this page...
...to populate the fields in Carousel seen here.
Login with SSO only can be turned on or off, based on your own preferences.
Selecting the SSO ONLY toggle will configure the system so that only site admins will be able to log in using an email/password.
Right-click "View Details", select "Open in new tab".
Copy the X.509 certificate in the clipboard...
…and in Carousel paste the certificate in the corresponding field. You may also add a logo if desired. Click Save.
Go back to the OneLogin page, click Save.
Go to OneLogin -> Administration -> Users, you may now assign the Carousel App to your users.
Congratulations! You can now use OneLogin Single Sign On to log into your Carousel server.