You've got it all backwards.

A detailed tutorial on how to turn a single digital photograph into a realistic looking polaroid montage.

1. Open your desired photo in photoshop
2. Duplicate the background layer (Layer => Duplicate Layer...)
3. Add a slight bevel to layer (Layer => Layer Style => Bevel and Emboss...)
4. Create a new layer (Layer => New => Layer... ; Shift-command-N)
5. Create a polaroid frame template
   1. With the rectangular selection tool create a vertical rectangle
   2. Fill with white (Edit => Fill ; shift-F5)
   3. With the rectangular selection tool create a square inside your white rectangle
   4. Fill with black (Edit => Fill ; shift-F5)
6. Add a drop shadow to layer (Layer => Layer Style => Drop Shadow...)
7. Select all layers excluding the background
8. Group Layers (Layers => Group Layers ; command-G)
9. Repeat the following steps until the image is covered with polaroid frames:
   1. Duplicate group (Layer => Duplicate Group...)
   2. Open group, if not already open, by clicking small triangle on left side of group
   3. Select the polaroid layer
   4. With the position tool selected move the frame to a new location (v)
   5. Slightly rotate the frame (Edit => Transform => Rotate)
   6. Select the image layer
   7. With the position tool selected slightly nudge the image using arrow keys (v)
   8. Slightly rotate the image (Edit => Transform => Rotate)
   9. Slightly scale the image proportionally (Edit => Transform => Scale)
   10. Hide the image layer by clicking the eye on the left side of the layer
10. Repeat the following steps for all groups
    1. Select the polaroid layer
    2. With the magic wand selected click inside the black of the template (w)
    3. Expand the selection by one pixel (Select => Modify => Expand...)
    4. Invert the selection (Select => Inverse ; shift-command-I)
    5. Show the image layer by clicking the eye on the left side of the layer
    6. Drag the image layer above the polaroid template layer within the group
    7. Delete the selection (delete)
    8. Merge the grouped layers together (Layer => Merge Group ; command-E)
    9. Hide newly created layer by clicking eye on left side of layer
11. Unhide all layers by clicking on the eyes to the left of the hidden layers
12. Rearrange layers to give the best perspective on photograph
13. Select the background layer
14. Select the entire layer (Select => All ; command-A)
15. Fill with white (Edit => Fill ; shift-F5)