First: You are going to need either a flat file to store the text, or a database scheme like MySQL.
Second: Create an HTML form that posts to a page that writes the output to the flat file or to the database.
Third: On the user's home page, call the unique identifier from the file or DB and retrieve the contents.
There are a lot of factors that go into how you go about this, including whether you want to do it as a flat file or DB, how you are uniquely identifying the user, etc.... Too many variables to just put up some generic code, depending on your needs. In any respect, everything you want to do can be found in the MySQL and PHP manuals...