this addweapon "weapon name" without the quotes. You will then also need This addmagazine "weapon magazine" without the quotes. Info for which weapons and magazine names can be found at http://community.bistudio.com/wiki/ArmA:_Weapons
~~EDIT~~ also, i forgot, you might need to put "removeallweapons this" without quotes in before you add weapons to make sure it goes correctly.
~~EDIT2~~ and, there might be different commands to add more then 1 magazine easier then the way I do it, but for my simple mind, I just do the addmagazine thing multiple times, since 1 command only adds 1 magazine.