Step 1:
Both papers are about 20x20 centimeters and white on the backside.
Prefold in half
 

Step 6:
Fold the edges to the centerline.

Step 5:
Prefold in half.

Step 2:
Prefold the edges to the centerline

Step 4:
Prefold the brown parts in half

Step 3:
Fold to the prefolded lines, see arrows

Step 10:
Repeat step 9 two more times.

Step 8:
Fold to the centerline one more time.
Then unfold the folds of steps 6 to 8

Step 9:
Fold these two edges towards each other

Step 7:
Fold the edges to the centerline.

Step 16:
Fold into a straight angle.

Step 15:
Repeat steps 12 to 14 on the left.

Step 12:
Fold this edge upwards over the prefolded line

Step 11:
Prefold these lines into the right direction (=mountain-folds).
Then turn the model.

Step 14:
Fold the other edges upwards too.

Step 13:
Fold this edge upwards.

Step 21:
Fold the edge downwards over the prefolded lines.

Step 19:
Pull the edges open, see arrows as example.

Step 20:
Turn the model again.

Step 18:
Turn the model.

Step 17:
Fold into a straight angle.
Repeat steps 16 and 17 on the other side, see arrow.

Step 22:
Slide / press the lower edge into the openings indicated by the arrows.

Step 25:
Fold over these three lines, start with the line on the right.

Step 26:
The white edge you created in step 25 is on the left in this picture.
Fold the red paper around the bar.

Step 24:
Done.....

Step 23:
Making sharp folding lines on the outside of the model keeps the model into the right shape.
Turn the model again.

Step 27:
Press flat and make about three valley-folds, start with the one on the right.
These folds hold the wrapping around the chocolate bar.