To change the number of player slots (amount of player able to join) you need to
- go to the file management tab in the sever panel
- Click on the severs folder
- Click on the default folder
- Click on the server folder
- Click on the commands.dat file
- This opens up in a text document
- From there you can type in this
- maxplayers (number of slots here) - without any brackets
- it is best to only have 24 as the server performs best with this slot count
- click save and restart the server