A flag isn't something you can add to an ammocrate (as far as I know). But there is a method that you can use I think.
- Create a soldier and name it player.
- Create a flagpole and in it's init write: this setflagTexture "rus_vlajka.pac"; this setpos [(getpos this select 0),(getpos this select 1),-10]; Name the flagpole: "vlajkaRUS".
- Create an ammocrate and name it "crate".
- Create a trigger and in it's condition put: ((player distance crate) < 5), in the on Activation Field put:
player addAction ["Take Flag","flag.sqs"];
- Create a file "flag.sqs" and put this code in it: vlajkaRus setFlagOwner player;
The player gets the flag now.