I upgraded to El Capitan yesterday, but it seems I'm almost getting used to changing the input source by shortcut "command + space" in previous versions and I have to use "control + space" to do that instead. I tried to change it but do not know the method. I want to revert back to the shortcut I used in Mavericks with "command + space" to change the input source.
If you want to change the language input source shortcut in El Capitan, just click on the shortcut check then press any combination you'd like (make sure it is not conflicting with other functions).