Players leaved during pvp will be killed. Timers are automatically set at the start of a fight.
All messages and labels are fully customizable. Configure file properties.yml.

/pvpt set < player> < time> - Set pvp timer to player.
/pvpt remove < player> - Remove pvp timer from player.
/pvpt look < player> - See the remaining pvp time.
/pvpt removeall - Remove all pvp timers.
/pvpt off - Temporarily disable pvp timers system.
/pvpt on - Enable pvp timers system.
Add permission to access all commands - amspvptimer.admin.

You can use static methods from AmsPvPTimerAPI.java class.
It also has two custom events: PlayerJoinPvPModeEvent and PlayerleavePvPModeEvent.
See more in the documentation.