How would I make a basic command?

FiveM Resource Development & Modding Discussion
4

client:

RegisterNetEvent('EventName')
AddEventHandler('EventName', function()
	TriggerEvent("chatMessage", "Sender Name", {150, 50, 180}, "text to send")
end)

server:

AddEventHandler('chatMessage', function(player, playerName, message)
    if message:sub(1) == '/test' then
        TriggerClientEvent('EventName', player)
        CancelEvent()
    end
end)

Edit for your liking
I also believe this has all you need