Man, you have some serius problem regarding reading comprehension. From the very same guide:
Quote:Address already in use
You get this error message if you try to launch proftpd when there's another running program that is listening to port 21. The two main reasons for this are either: (1) You have a previously launched proftpd instance running or (2) There's another program interfering, like inetd/xinetd.
The easiest method to see which program is blocking the ftp port is by using netstat. Executing ”netstat -tlnp | grep 21” will give you some output like this:
tcp 0 0 0.0.0.0:21 0.0.0.0:* LISTEN 10659/proftpd: (acc
On the right side of this output you can see which pid/program_name is listening on this port. If it's proftpd, try to stop the service (usually /etc/init.d/proftpd stop) and re-execute this command to check that it has disappeared. If it stays, get more aggressive by directly killing the proceess (kill -09 <pid>).
If the program shown listening on this port is inetd/xinetd, you should deactivate this service on it's configuration (very system dependant) or, even better, totally get rid of it all
Once there are no processes listening on this port, you can retry executing proftpd in debug mode as in the beggining and proceed from here