May 23, 2018 - Ubuntu 17.10, Ubuntu 18.04 (and above) come with Python 3.6 by default. You should be able to. Finally you can then install Python and Pip.
To install a Python package, you need to be in the command line as @MohideenibnMohammed suggested. You cannot install a package from within a Python script using pip. You have installed Python 3.6.1 which will have pip already installed so you don't need to try and install that again. Next, you need to make sure that Python is added to your PATH. Open Start Menu and right click My Computer. Click on Advanced System Settings.
Click on Environment Variables. Find the system PATH variable and click Edit. You want to add Python to this PATH variable by adding exactly;C: Python36 (assuming that is where you installed Python) Go back to the command line and type in pip install numpy (you can use pip3 instead of pip if you wish).