ok
some basics:
for instance, my setup is;
– one set of all the wordpress directories and files on my computer;
– a second set of the files on ther server.
when i want to change something, i edit the files on my computer, save them and the upload the changed files to the server.
i work with ‘dreamweaver’, but there are other free programs available from the internet.
i suppose many others here in the forum do the same.
i know you can change wordpress files in the admin area, that is just not the way i do it.
there are many free articles on the web how to learn to customize wordpress themes, i suggest you start reading some of them, and then come back to the forum.
it is great that you have the idea and the ambition to get all these things done, however, a basic knowledge is important to have.