Press CMD + space (ie open Spotlight), type terminal (or go to Applications/Terminal). Terminal will open.
Operating systems do not come without a terminal emulator (a program that lets you access the command shell using typed commands). The one that comes out of the box on OSX is called Terminal (as it is on most Linux distributions and Android and IOS and as it is now on Windows [used to be called Console]).
It’s just a UI that lets you control the computer, exactly the same as the graphic windowed UI you normally use when doing anything on your Mac.
PyCharm isn’t an alternative, PyCharm is an IDE, it’s a fancy text editing program. It doesn’t care whether you’ve (for example) installed libraries by using some installation program or by dragging files around in your GUI windows or by using a text command to do the same thing in a terminal, it’s all exactly the same thing.
PyCharm itself has a terminal emulator (note: as long as you’re not using the education version of PyCharm), which you access using Alt + F12. Open that if you want instead of the system one, it’s the same thing. It’ll just be a bit cramped because it’ll open as a panel in PyCharm rather than in a different window, might be hard to read.
You ain’t got a choice here I’m afraid: if you are doing any development work at all, you are likely to be hamstrung if you don’t know the basics of how to use a terminal.