Open your design in Canva
Select the photo, video, or element you want to overlay
Click Edit image or use the top toolbar options
Choose Adjust if you want to change transparency, brightness, or tint
Add a shape or rectangle from Elements
Resize the shape to cover the area you want
Click the color box in the toolbar
Select the color you want for the overlay
Adjust transparency using the Transparency icon
Position the overlay layer above the image if needed
Use Arrange to move the overlay forward or backward
Group the overlay with other elements if desired
Download or share your design when finished