MyBB Community Forums

Hey my forums are still version very old and im wondering how I must update them to the new 1.6.x. I wont lose post etc?

No, just the download the latest MyBB package, and upload to your server using FTP client and replace every files and go to http://yoursite.com/install/upgrade.php

which version you are using ? if you follow the documentation then you will not lose any of earlier posts.
However to be on safe side, it is always better to keep a complete backup until you are confident ...

It wouldn't be called upgrading if you lost your posts every time Make sure you have backups and you'll be fine.