I want make a random player changes her unit. how i do that?
Please elaborate further. Do you mean that you want a script command to change his/her unit correct?
You can see the Zombie Tag template for an example of a script that randomly selects a player.
To randomly select a player and change their unit, you can set a global variable to a number of a random player and count down with the variable until the player with that number is found.
This is every second?
Run the script with whatever trigger you need. You could use every second if you need a random player to be chosen for whatever purpose every second.
Can i use like a for all players with seting unit and break loop?
You can use break out of the loop
in a for all players in a player group
action to stop searching the players once you’ve already found a player matching a criteria, for example. I’m not exactly sure what you mean in your question… What is “seting unit”?