You can put as much thought into the placement of the weapons you want in your level. The placement of the weapons you choose can drastically effect how the level plays out. For example, placing a rocket launcher in the middle of a large room will entice a player to seek out and attempt to pick it up, however it leaves them extremely vulnerable to attack. Since the room is empty and relatively large there will be no place for the player to hide or run once they pick up the weapon. This makes the placement of the rocket launcher both easily accessible and extremely dangerous to get. Any player that attempts to pick up the rocket launcher can be easily killed.
Now if you place the weapon in a well hidden area or in a spot that provides cover (behind a metal crate for example), it becomes easily accessible, hard to find and relatively safe to pick up.
Once you have decided on a place to put the weapon, open up the generic browser. On the generic browser window click the Actors tab. This will show you a list of a lot of different actors that we can place into our level. Actors are objects that you place inside the level in which players can interact with, such as weapons, ammo, health vials and vehicles. For now, all we are concerned with is the NavigationPoint actors.

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Click the small + sign to roll out the category. Inside this category click the + sign beside PickupFactory. In the PickupFactory category you see 4 more categories and one that is labeled UTWeaponPickupFactory which does not have the + sign beside it. Since we are placing a weapon, go ahead and click on the bold UTWeaponPickupFactory text.
Once you have selected that it is now time to place it into the game. You accomplish this by simply right

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clicking on any part of your levels floor. Doing this will pop up a rollout menu, inside the menu click Add UTWeaponPickupFactory Here. You will notice that the actor has been placed in your level. Now all we need to do is to set the type of weapon that it will allow us to pick up. We do this by double clicking on the actor itself. A new popup window called UTWeaponPickupFactory_1 Properties will show us a complete list of all of the properties of the actor.
Clicking on the UTWeaponPickupFactory will give us a list of weapons that we can add to the actor. Select any weapon that you like and the next time you run your game, the weapon you choose will be shown.