在PyCharm中安装FreeSimpleGUI时遭遇pip未被识别错误的求助

各位大佬好，我最近在PyCharm里尝试安装FreeSimpleGUI这个库，结果刚运行安装命令就碰上个棘手的问题。

我输入的安装命令是：
pip install FreeSimpleGUI

紧接着就弹出了如下的错误提示：

pip : The term 'pip' is not recognized as the name of a cmdlet, function, script file, or operable program. Check the spelling of the name, or if a path was included, verify that the path is correct and try again.
At line:1 char:1

• pip install FreeSimpleGUI

• + CategoryInfo          : ObjectNotFound: (pip:String) [], CommandNotFoundException
  + FullyQualifiedErrorId : CommandNotFoundException
  

我就是想顺利装上FreeSimpleGUI来用，结果被这个“pip未被识别”的问题卡在这里了，有没有朋友能教教我该怎么解决这个问题呀？

备注：内容来源于stack exchange，提问作者Emmanuel Adu