All three layers are of different sizes, opacity and Blending modes. On the right side is smaller than on the left. Near the fungus – smallest. Try to make the size of bokeh proportional.
The next step is to create a blurred background. Select a groups with the background, mushrooms and animals and layer with bokeh. Duplicate them (Cmd/Ctrl+ J). Combine doubles in a single layer (Cmd/Ctrl+ E).
Go to Filter > Blur > Gaussian Blur… Set the radius 3.0px.
On blurred layer add a layer mask, used a soft brush to remove the blur from center, animals and fungi edges. Dark part of the frog leave blurred.
I created a brush to paint a small cloud of particles near the mushrooms. Original brush was a soft brush. Save a Brush.
Create a new layer uppermost. Take your brush and draw near the small mushroom cloud. Set Opacity 80%.
That they add to the glow layer style Outer Glow with the settings as shown in Figure.
All done! I congratulate you! I hope you learned a lot and you were a pleasure to read and learn my tutorial. Here is ready to work with all layers. Check it out!