Automaticall upgrade won’t function

Each time i try to update a plugin, or wp itself, i get a dialog just like this lines explains:

Note that your files all need to be owned by the user under which your Apache server executes, or you will receive a dialog box asking for “connection information,” and you will find that no matter what you enter, it won’t work.

But what can i do to fix permissions? I already fixed them from my host’s CPanel, and it won’t work. I cannot upgrade wp to 2.8.4 because i get a connection error in my browser (not in wp, neither in my database, but in the browser).