"its a trigger"
Wrong, it's an effect (tribute to Oddy).
"look under change name click the unit you want and type the name."
Wrong, he wants the player's name to change, which is a variable. You can request this variable by filling it in the name field in the Change Name effect:
{playername(1)}
Will return player 1's name, and similar for the other players. You can also combine it with other stuff like:
Change name: {playername(1)}'s dog.
Send spoofed chat: {playername(1)} sux0rz
Send spoofed chat: Hello, if you're not {playername(1)} then you must be {playername(2)}, {playername(3)} or {playername(4)}! W00t, I rule!
"but be carefull because it aplies to all of those units."
Wrong, only to the specific unit you select.