Kivy is a python module, you need to install if you want to use it.
If you are using python3 try, pip3 install kivy, if is python2 just pip install kivy

First make sure python tools are up-to-date:

python -m pip install --upgrade pip wheel setuptools

Then install python dependencies for kivi

python -m pip install docutils pygments pypiwin32 kivy.deps.sdl2 kivy.deps.glew kivy

ModuleNotFoundError                       Traceback (most recent call last)
<ipython-input-2-83e5acb1d5ec> in <module>
----> 1 import kivy
      2 
      3 from kivy.app import App
      4 from kivy.uix.label import Label
      5 
ModuleNotFoundError: No module named 'kivy'