Select extensions then search python, it should be the first extension. It's the one made by Microsoft.
Then select install
This will take a few minutes
You will then see a window that has a few options that include
install python
select python interpreter
run your python code
...
Select the "select python interpreter" option then select the recommended option. This is where python is installed on the school computer. You shouldn't have to worry about it after this first set up.
If you're at home you may need to add python to your file path. By following the instructions on the site here:
https://www.educative.io/edpresso/how-to-add-python-to-path-variable-in-windows
If you get stuck talk to your teacher.