How do I use% p and% f correctly in postgresql.conf to register in advance?

I am trying to modify postgresql.conf (Postgre SQL 10.0 in Ubuntu 18.04 VPS) to configure the advance write log (WAL).

AIUI, the commands should be:

wal_level = replica             # minimal, replica, or logical
archive_mode = on               # enables archiving; off, on, or always
                                # (change requires restart)
archive_command = 'cp %p /var/lib/postgresql/10/main/pg_wal/%f'          
archive_timeout = 600           # force a logfile segment switch after this
                                # number of seconds; 0 disables

AIUI,% p refers to the database file (to be archived) and% f refers to the file name that will contain the copy of that database file.

In this case: I am telling you to copy the database file every 5 minutes to the / pg_wal directory.

However, this is clearly not correct as the error log files show:

cp: 'pg_wal/000000010000000000000002' and '/var/lib/postgresql/10/main/pg_wal/000000010000000000000002' are the same file
2020-02-16 21:01:05.857 UTC (20707) LOG:  archive command failed with exit code 1
2020-02-16 21:01:05.857 UTC (20707) DETAIL:  The failed archive command was: cp pg_wal/000000010000000000000002 /var/lib/postgresql/10/main/pg_wal/000000010000000000000002

Therefore, I am not sure how% p and / or% f should be used. If someone could present the syntax, I would be very grateful.