Sparroow

I set up a spawn for my server and I used barriers so no one would get in and kill the cows, but people keep spawning in those barriers. How do I make it so that people only spawn on the pressure plate I set down?

So I'm hosting a server for this discord server I'm in and I'm trying to set up warp, home, and tpa permissions for everyone, but I can't find where to put the permissions and where to make the groups. Any help?