update MacBook UserGuide

docs/assignments/ISAGeekClub/MacBook_UserGuide/UserGuide.md

+# How to use Pycharm and VS Code on MacBook Air
+
+## Tips:
+
+**For screenshot**:
+
+`Command + Shift + 4（截取部分屏幕）`;
+
+`Command + Shift + 3（截取整个屏幕）`
+
+## Issue Solved: _Command not found:python_
+
+When you typed `python` in the terminal, it returned this error:
+![alt text](<Screenshot 2024-10-15 at 17.38.20-1.png>)
+
+It probably means the system didn't install python, you can try `python3`:
+
+![alt text](<Screenshot 2024-10-15 at 17.51.34-1.png>)
+
+In this case, if you need install the third party package, you can use `pip3 install <package>`
+see an example on installing _pygame_ package.
+
+![alt text](<Screenshot 2024-10-15 at 17.53.59.png>)