I upgraded to the new version of Pycharm. In the terminal, it says bash-3.2$ instead of my username. When I tried to install a library, it said that pip command is not found:

bash: pip: command not found

So I installed pip:

bash-3.2$ sudo easy_install pip
Searching for pip
Best match: pip 8.1.2
pip 8.1.2 is already the active version in easy-install.pth
Installing pip script to /usr/local/bin
Installing pip3.5 script to /usr/local/bin
Installing pip3 script to /usr/local/binUsing /Library/Python/2.7/site-packages
Processing dependencies for pip
Finished processing dependencies for pip</i>

Okay, now all I have to do is use pip to install a library, right?

But then, this happens:

bash-3.2$ pip install pandas
bash: pip: command not found

I don't understand what I have to do to actually install pip. Or should I use sudo easy_install [library]?

I know that this is not precisely what you're asking, but PyCharm has its own built-in package manager. You should not have to use pip manually.

File->Settings->Project Interpreter https://www.jetbrains.com/help/pycharm/2016.3/installing-uninstalling-and-upgrading-packages.html

there you can manage the installed packages for the selected Python interpreter or virtualenv.