Alright, it's quite simple then.
Do these steps from your computer:
Download the latest IPS version package,
Extract the archive,
Delete unnecessary files (anything related to nulled software, like validators, or readme files),
Rename your admin directory if you changed in your server,
Archive it back in ZIP, don't forget to do this from root directory,
Transfer the archive to your server
Continue from your server
Move your archive to the root directory (generally it's /var/www/html)
Type 'unzip <archivename>.zip'
Press A to confirm to overwrite all files
Don't forget to backup your database and files first! You can simply backup files with ZIP command and database with phpMyAdmin database output.
