Your first program

Ok, you installed python from www.python.org
The version 3.5 is good.
Now open the window console (as I will speak about the windows version version, even if python works in almost the same way in linux and MacOs systems).
To open the command line, click on the windows button + r, then write cmd and you are done.
After that write python and you will see that you are ready to start.
The console will show you some informations about the version of python.

First program

write this:
>>> print("Hello World")

Then click enter and you will see your first program appear.

You second program

Let's make another program

>>> a = 1
>>> print(a)
1

In this one you created a variable called a and you gave a numeric value (1).
After that you printed to the console the number.

Let's write on a file

You can easily put your values in a file instead of using the console to display your data.

>>>with open("newfile.txt","w") as file:
...    a = 1
...    file.write(a)
...

Ok, after you clicked enter a couple of time, go check in the directory where you are to find the new file you created with the number 1 in it. Great Stuff.