Study the three images of Jesus on the manuscript, noting their positions and the direction in which each cross points.

 
The blank spaces on the wall puzzle are lined up in the same way, so assume that the crosses on the manuscript fit into these spaces.
 

 
Analyze the crosses in the top and bottom rows to find a pattern to their directions.
 
 

TOP ROW

 
The first cross is pointing upward. The second cross is rotated once anti-clockwise. Similarly, the third and fourth crosses also rotate once anti-clockwise. After each rotation a cross will point in one of eight directions corresponding to an octagon. 
  
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BOTTOM ROW

 
The first cross again points upward. Although the second cross also rotates anti-clockwise, it does a triple rotation and points at a direction 'three' sides from the first. The same pattern applies to the third and fourth crosses. 
   
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Now work out the settings for the crosses in the middle row. 
  

MIDDLE ROW

 
There's a single anti-clockwise rotation between crosses in the top row and a triple anti-clockwise rotation between those in the bottom row. Accordingly, there must be a double anti-clockwise rotation between the middle row crosses. From the direction in which the second cross points, you can work out the others. 
  
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