check the command reference for how to remove weapons from units and how to put stuff into crates. To get the name of the weapon from an addon, you have 2 options -
a) read the readme for the addon, it should be in there
b) set a trigger to radio alpha, on activation
hint format ((weapons <unitname>) select 0)
then make your soldier with the addon with the name you chose.
Something like that, I might have the syntax wrong but I'm sure someone will correct me if it is.