Unable to install apps from Windows 10 store

When you already choose the app in Windows 10 Store but the button for downloading is not active and it say 'Powered by great new features in the lates Windows update. Get it now at https://aka.ms/winup', what have to do ?.

It means that your Windows computer need to update. Follow the URL provided (https://aka.ms/winup') to download Windows 10 Update Assistant.
Run  Windows 10 Update Assistant to get update of Windows 10.

After updating, the not active download button will change to active.