1) Open your coat of arms document in photoshop.

2) Flatten Image. When working with the pen tool and various other tools, a new layer is created. It makes it impossible to edit the shape so we will need to Flatten our Image often.
>Layers
>Flatten Image

Note: Don't flatten until you have created and moved your triangles in place.
3) Select a color. Double click on the foreground color. A color window appears. Select the color. Press OK.

4) Create a triangle.
Select the polygon tool.
Type 3 in the sides in the menu at the top of the screen.
Create the triangle away from the shield.
Select the magic wand tool and select the triangle.

5) Copy the triangle.
>Edit
>Copy
>Edit
>Paste
6) Resize the new triangle.
Select the move tool.

It looks like there is just one triangle. When you copy and paste, it simple pastes the new triangle directly on top of the original one. Using the move tool, select the triangle and move it away.
Select it.
>Edit
>Transform
>Scale
Put your finger on the shift key (this keeps the constraints. i.e. similar) and make the triangle much smaller.
Select any tool. Apply.
Using the magic wand tool, select the small triangle and copy and paste it two times. I rotated one of my triangles.
Move the triangles in place.
Flatten image.

5) Create elements for the other two quarters. I'm creating lines.