1. Installing Python and running Hello World

Download Python and install it on your system. I am working on Windows so installed it on Windows.
Downlod link for Python.
Few screenshots taken during installation:
installing Python

installing Python

Once Python is installed successfully, open Notepad and type:
print ('Hello World')
installing Python

Save the above Notepad file with .py extension. For example I saved it as 'firstcode.py'.
Open Command prompt and go to the location (I saved it on my desktop) where firstcode.py is saved on your system. To run the code, type py [NAME_OF_THE_FILE] and hit Enter.
installing Python

Few points to consider:
1. The code we wrote is calling built-in function called 'print' and NOT 'Print'. No capital p, else it will show an error like:
installing Python

2. To know the version of the Python installed, type py on the Command prompt and press Enter.
installing Python

To go to the Command prompt again, type quit or (exit()) and hit Enter.
installing Python

3. Above, we wrote the Python code in file and ran that. You can also wirte the Python snippet directly in the terminal window like:
installing Python

As you can see in the screenshot above, we first went to Python prompt by typing py and then wrote the snippet which prints Hello World and then hit Enter.