Plugin Help World Guard API (Help)

Hey everybody. I was working on a bosses plugin and wanted to make sure the player spawning the boss is in a certain region. I have seen lots of tutorials online, but they never answer what I need help with. If you do give me an answer, please give me a good explanation so I can really understand it.

This is my best guess at the moment(Also how I want it to be formatted):

Code:

if(!(p.isInsideRegion("Boss"))) {
p.sendMessage(Utils.color(Main.getPrefix() + "&cYou Can Only Spawn This In The Mob Arena!"))
return;
}

I know this is dead simple but I am new to using worldguard api.