I hope today finds you well. Please see the below link on associating an image gallery with a content item with the latest release of Sitefinity.
You might also find this blog post helpful.
Let me know if you continue to have problems implementing this solution. It is a little tricky but it can be done.
the Telerik team
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items