yeah, macropod is absolutely right. I think there's no other way. You need to open format menu and choose pic. Then click on the layout tab and choose your wrapping style. This will allow you to move your pic around the document. And then you insert your 2nd pic which you want to take place on top of the first one. Right? Select the 2nd one and wrap it again. Now you can drag the 2nd one on top of the first.
Macropod was in brief. I explained because if you find it difficult.