Record the current server setup
Note the Minecraft version, loader, active mod list and startup command. Confirm which directory the server actually uses. If you manage the server through a panel, check the instance settings before uploading files.
Install during a planned restart
Back up the world and configuration while the server is stopped. Select the matching Clumps build using the official file details, then copy it into the active mods folder. Keep the previous file separately if this is an update and record exactly what changed.
Check with a small player group
Start the server and review its log before opening access to everyone. Test a familiar XP collection area with a small number of players, keeping other activities similar to your baseline. Save any errors and the full installed filename. If you need to undo the change, stop the server first and return to the previous mod file and configuration, using the backup if world recovery is necessary.
Next step: read the installation guide or find a matching download.
Project reference: Official Clumps project and file details.