To install UI for Xamarin on your machine from the Windows Installer MSI file, follow the instructions below:
Log into your Telerik account and click on Downloads from the top menu.
In the list with all available products find UI for Xamarin Cross-Platform, and click on it. This will open the page with all available downloads for the product.
Here you can download the automatic installation (MSI) file. Or the ZIP file with the dlls.
Once the download completes, run the MSI file and follow the instructions. On a 32bit machine the wizard will install the UI for Xamarin component in the following folder unless you specify otherwise: C:\Program Files\Telerik\ or C:\Program Files (x86)\Telerik\ for a 64bit machine.
If you prefer using the ZIP file with the dlls instead of the automatic installation you can check the Manual Installation for Visual Studio help article.