Telerik UI for ASP.NET are added automatically to the Visual Studio Toolbox during installation.
The easiest way to setup the Telerik controls in your toolbox is to use the Telerik Toolbox Configuration Wizard.
If you are using the ZIP distribution, however, you can do this manually by following the steps below:
Open your application in Visual Studio.
Expand the Toolbox.
Expand the General section. Alternatively, you can create a new section by selecting the Add Tab option from the context menu (right click anywhere in the toolbox). When the new tab is added you can choose its name (e.g. Telerik UI for ASP.NET AJAX RX YYYY .NET 4.0).
Right-click in the General section (or the new one you just created) and open Choose Items.
On the .NET Framework Components tab, click Browse.
Browse to the installation folder, open the Bin40 folder and select the Telerik.Web.UI.dll.
If the Windows Installer MSI Package was used to install Telerik UI for ASP.NET AJAX, the bin40 folder is located in C:\Program Files (x86)\Progress\Telerik UI for ASP.NET AJAX RX YYYY\Bin40
If the ZIP was used to install the Telerik controls, the Bin40 folder is located in the folder where the installation files have been unzipped.
If you want to add Telerik controls for .NET 3.5 or .NET 4.5 web project you should select the Telerik.Web.UI.dll from the C:\Program Files (x86)\Progress\UI for ASP.NET AJAX RX YYYY\Bin35 or ~/Bin45 folder.
If the controls do not appear in the ToolBox, please make sure that the project is of type ASP.NET Web Forms site/ application.
Telerik controls are not automatically installed into any configuration of Visual Studio Express because the end-user license agreement (EULA) of VS Express does not allow third-party extensions to be registered.
Add the controls to your project
The following article describes the steps for including the Telerik Assemblies into Visual Studio projects: Add the Controls to Your Project