How to import python external libraries into a project,

I am writing a python using Intellij but I am having issues importing external libraries, and in this case it is matplotlib which I installed using pip. The instructions I read are mostly related to Java and not python. What is the proper way to include these libraries ?

it is constantly asking me to install the package, but when I click install, nothing happens, still asking me to install matplotlib 



What is your IntelliJ version and interpreter type (virtualenv, conda env?)?

You can see the list of installed packages and install the needed ones from File | Project Structure... | SDKs --> choose the needed SDK and switch to Packages tab on the right.