Okay so I tried inputting code here that is supposed to kick but I keep getting errors?

playerToKick actually points to the player who fired your event! This is because the first argument to OnServerEvent connections is the player that the event was received from.

I can't help but notice that there's a security issue with your code. There's nothing that's stopping anybody, including hackers, from firing the RemoteKickEvent. It's a RemoteEvent in ReplicatedStorage, so it's visible to every player. Even if they can't see your GUI, hackers are going to figure the event out.

I'm going to restructure your code a bit.

Server code:

local allowed = {DevRhy = true, tellophase = true} -- Use dictionary format to make the check more efficient

game.Players.PlayerAdded:Connect(function(player)
    if allowed[player.Name] then
        script.RoKicker:Clone().Parent = player:WaitForChild("PlayerGui")
    end
end)

game.ReplicatedStorage.RemoteKickEvent.OnServerEvent:Connect(function(playerWhoRequested, playerToKick)
    if not allowed[playerWhoRequested.Name] then
        -- The player who requested the kick isn't on the allowed list.
        -- Definitely a hacker, so we don't react.
        return
    end
    local p = game.Players:FindFirstChild(playerToKick)
    p:Kick("You have been kicked.")
end) 

Client code:

local frame = script.Parent script.Parent.Buttons.KickPlayerButton.MouseButton1Click:Connect(function()
    if game.Players:FindFirstChild(frame.playerToKick.Text) then 
        game.ReplicatedStorage.RemoteKickEvent:FireServer(frame.playerToKick.Text) -- Here, we use .Text instead of passing frame.playerToKick (which is a local TextBox)
    end
end)