You must to add pip's path into Environment Variables. Pip is contained in python's script directory.
Example my case: C:\Python34\Scripts\pip.exe
To add path to environment variables.
- Hold Win and press Pause.
- Click Advanced System Settings.
- Click Environment Variables.
- Add
C:\Python34\Scripts
(Sorry I don't know name of python 3.5's directory) to the Path
on System variables.
- Restart Command Prompt.
Edit
In another way, you can use pip-Win instead of pip. Read more here: https://sites.google.com/site/pydatalog/python/pip-for-windows