How we can use python to develop softwares

Answer 1

Get an idea, learn what you need to make it, find the libraries required, and write the code

Answer 2

1st make sure what you want to build. Lets, for example, you want to make a calculator. So write the codes as you normally do to make the calculator. You may want to use tkinter for a nice GUI or matplotlib to a plot.
Now to ship it as a standalone software you need to bundle the python interpreter and all the required modules. There are quite a few options available for this job but my favorite is pyinstaller
https://www.pyinstaller.org