Step 1

Using Polygonal Lasso Tool to make a shape and fill the color #45862C like this:

Step 2

Continue to use Palygonal Lasso Tool to split that shape into 4 parts (each part in one layer)

Step 3

Now the most important is to radiate light upwards, you will pick Gradient tool and set the color like this: 45862c---------------------------------------b2d50c

Ctrl + click on layer No.1, use Gradient to drag like the result below.

Step 4

Continue to apply step 3 to 3 remain layers. You should get the effect to the left

Step 5

Create a new layer, zoom out the right angle of the shape then use Polygonal to draw a selection like the picture below: Pick Gradient tool and set the color like this:

Step 6

Apply gradient to the selection, you will get the result to the left

Step 7

Continue to apply step 4 to 3 remain layers, you will have the result to the left

Step 8

Final step, you will make shadow around the logo, and this is my final result: