When you buy an exclusive chest in army men strike, where do you go to open it?

When you mean exclusive chest... do you mean something you buy with real life money? If so, the chest is automatically opened the moment you buy it.

If you're referring to exclusive officer chests, then simply do this:

1) On the bottom of your screen inside the game, click the "Items" tab

2) Scroll through your items until you see the chest you're interested in

3) Click the chest and press "Use" to open it

Feel free to reply if you have anymore questions!