Whoa, um, type "hi".
Really, I don't follow your question at all. What do you type for what? PREFIX is simply a reference to your location of your apache conf files, maybe /etc/apache/conf/httpd.conf What to type in vi to start editing is an 'i' and to save type "ESC" then "wq!" to write the file and quit. Otherwise, I don't know what to tell you.