Imagine a concept for your scene - for me it was "tiger loose on San Francisco streets"
Gather photographs; Google Image Search is helpful
keywords can help; for me "tiger standing up" was more helpful than just tiger
you can use the Tools button to constrain your search by, say, large size pictures
try to get big, high resolution photographs with lots of pixels! It's better to shrink than it is to enlarge!
Using Photopea or Photoshop, open the photograph that will be your background
You can do some Image Editing like Levels, Curves, Brightness/Contrast, Shadows, etc. in the menus if you like
then use Image menu, Image Size... to make it 300 DPI and at least 10 inches wide or tall... it might be already!
Use View menu for Zooming in and out; shortcuts are Command + to Zoom In, Command - to Zoom Out, space bar to pan
Using the various Selection tools and the adding (shift key) and subtracting (option+shift keys) abilities, select sections of the image to be in the foreground
Layer menu, New submenu, Layer via Copy for each selection
Select menu, Deselect if you mess up your selection and want to start over
File menu, Save as PSD often!
For each image you add, File menu, Open the image
edit the image settings if you like such as Levels and Curves and others
use the Selection tools to select what you want
Edit menu, Copy the selection, go back to your scene, and Edit menu, Paste
Use Edit menu, Free Transform to resize it to taste (press return or enter key when done!)
File menu, Save as PSD one last time! Make sure it is moved to your Period folder if using a school computer
Go to Photopea or Photoshop, and File menu, Open... your PSD file from yesterday
Continue adding and editing selections from photos as you did yesterday!
Consider doing some tasteful Layer effects, such as Outer Glow or Drop Shadow
Consider adding Text? You can also do layer effects on text
Any last edits to do to any layers to make the composition more effective?
File menu, Save as PSD one last time! Make sure it is moved to your Period folder if using a school computer
File menu, Export as submenu, JPG to create an image for your Google Site page
On your Google Site, create a page called Photo Manipulation and Insert your manipulated JPG image
Add a What I Learned text section and write the story behind your image and also what you learned about photo manipulation in Photoshop or Photopea regarding making and changing selections, layers, layer effects, image formatting and editing and sizing
Push Publish and copy the link to the page and add the link to your Google Classroom assignment and turn in.