For server visitors:

Use:
/pass [password]
to enter the password. once the countdown is over and the right password has not been entered, the player will be kicked.

For admins (OP permission required):
Use:
/sp reload [logoutOps]
logoutOps: true/false, log out all OPs after reload.
to reload the plugin.


/spChangePw [oldPwd] [newPwd]
Change the password.

Furthermore:
The different messages and timer can be changed in the config.yml.