There are two ways to attach a weapon. Either you make it with a spell, or I can tell you how to do it with GUI triggering. If you need it attached to only one unit, let's say immidiately at the start of the map, make a new trigger, then for "Event" put in "Meelee initialization", then for "Action" search "Special Effect"- then click on it, then it will ask which unit you want it to attach to, click on unit then select the unit you wanna attach to, then select the special effect you want attached (it will be under the imported thingies) then for the attachement point, write in either "hand, right" or "weapon". sry I didn't post pix, but I was lazy. If you need them, I'll make some.