upload your index.html page which is what your homepage needs to be and make sure it is in your root directory not in a index_files folder
some people have a tendency to delete the place holder index.html page in the file manager area and name their page somethingsilly.html or home.html or something but your main page needs to be index.htm or index.html so either rename whatever you named your homepage to index.html and make sure as said it is in your root directory
or create index.html and have it redirect to the page you want to open. I do that because I use php pages and I want my index.php to open not the html.
You do not need to redirect index.html to index.php. A website will read an index.php the same as it reads index.html, so if you delete index.html and just have index.php it will work fine! :)