Where can I enable the Desktop Gadgets in Window 10?

Microsoft retired the Desktop Gadgets in Windows 8 to push the usage of Store Apps. The purpose of the gadgets are served by the Live Tiles that you can pin to Start/Start menu.

You can use 3rd party installers which bring back the Windows 7 sidebar if you really like them.

Download and run the setup,

click next and wait until the setup is finished. Now do a right click on the desktop to open the Gadgets again and drag & drop the requested gadgets to the desktop:

That's it, now your Gadgets are back on the desktop.

Consider also the Gadgetarian at

http://windowslivegadgets.com/gallery/317/enable-sidebar-gadgets-windows-8-metro/

Gadgetarian does not add any new abilities to Windows 10, it just enables the native gadget functions, now unfortunately hidden. This way you can keep using all of your old desktop gadgets or add new ones, without compromising the integrity of the OS.