To update your server go to:
https://github.com/TastyLollipop/OpenWorld
Click the latest release
And download the correct file for your Operating system
Unzip the files and move the newly unzipped files into your existing server
Check in the update announcement in #server-updates if you need a new server settings.txt
If not, your all good to load up the server and start playing again
If it does need a new server settings.txt, open the "extras" folder
Then "default setting files"
And then open the "server settings.txt"
Copy over your settings from the old version to the new
Then you can delete the old server settings.txt and replace it with the new one
Make sure you edit any new settings there may be in the new server settings.txt
Then the server is updated and your free to play