Hi Sun,
- Go to https://www.python.org/download/
- Assuming you have a Windows machine, scroll down to the bullet list, and select the first item -- Python 3.4.1 Windows x86 MSI Installer (Windows binary -- does not include source)
- Open Windows Explorer, navigate to your Download directory, and when you find the file "python-3.4.1.msi", double-click on the file to run the Python installer
For the installer, generally accepting all the defaults is fine.
From here, you are on your own. I can suggest buying or checking your library for a basic Python book -- I've always found the "... for Dummies" series to be good starters. But there are many others.
In addition, see the Python online documentation at https://docs.python.org/3/
As an alternative to installing Python on your computer, you can find Python online interpreters. One example is
http://www.compileonline.com/execute_python_online.php
This would be faster than installing on your machine, but would require that you always have Internet access when you want to run Python. Your choice.
I hope this helps you ! Good luck.