To make a Branded Content post on Facebook, your Facebook Page must be an approved Branded Content partner on your sponsor's Facebook Page.
Your sponsor will need to enter your Facebook Page name in the Approved Pages Box in the Brand Collabs Manager. This section is located in Page Settings under Branded Content.
To add a Branded Content sponsor to your post in SND, simply click the handshake icon in your Post Composer.
In the Branded Content search bar, type in the name of your Branded Content sponsor and select your sponsor for the drop down.