please read the documentation carefully, especially the section 22.3.2. Making a Base Backup and 22.3.3. Recovering with an On-line Backup.
You have to realize that you first need a online backup, to be able to make a point in time recovery. for a successful pitr, you need a online backup (or base backup) and all the archived wal's (or pg_xlogs) to the last possible point; this also includes the very last incomplete wal-file in $pgdata/pg_xlog.