Welcome in Sitefinity!
Please note that we do not recommend a direct use of the RadControls in our backend. You need to wrap them in a user control. Please take a look at this help article
for more information.
Let me know if you need further assistance.
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