[H] Locating every player on my server from a textbox and using a textbutton to kill or ban someone?

I'm trying to make some sort of admin gui for my game where I would type in a player's name onto a textbox, and when I click on a textbutton (for example, to kill or ban someone) it would kill or ban them from the server. I've tried searching for an exact topic like this for ~2 hours and found nothing related to this, and any other thread mentioning the textbox thing are just really confusing for me.

Here's an example on what I'm trying to talk about