for documentation, please take a look at the video or take a look at this below:

Installation:
    Download the image_overlay.py file
    In Blender, go to Edit → Preferences → Add-ons
    Click Install and select the downloaded file
    Enable the add-on by checking the box next to "Image Overlay"

Interface Location:
Find the Image Overlay panel in the 3D Viewport sidebar (press N if hidden) under the "Image-Overlay" tab.
Quick Start Guide
Step 1: Set Up Your Image Folder
    In the panel, navigate to "Image Folder Setup"
    Click the folder icon and select a folder containing your reference images
        Supported formats: PNG, JPG, JPEG, TGA, BMP, TIF, TIFF, EXR, WEBP
    Click the refresh button (⟳) to scan the folder

Step 2: Add Images
Option A: Add All Images
    Click "Add All Images" to load every image from the folder

Option B: Add Single Image
    Select an image from the "Available Images" dropdown
    Click "Add Selected Image"

Step 3: Display Settings
Choose where to display your overlays:
    3D Viewport: Shows images while modeling/sculpting
    Image Editor: Shows images while texturing/painting

Working with Images
Managing the Image List:
    Enable/Disable: Check/uncheck the box next to each image
    Select: Click on an image name to make it active for editing
    Remove: Click the X button next to any image
    Clear All: Remove all images with the "Clear All" button

Image Properties (Selected Image)
When an image is selected, you can adjust:
Size:
    Drag the slider or input a value (10-1000 pixels)

Position:
    X: Horizontal position from left edge
    Y: Vertical position from bottom edge

Opacity:
    Controls transparency (0 = invisible, 1 = fully visible)

Quick Positioning Presets:
For the selected image, use these one-click buttons:

    Top-Left, Top-Right, Bottom-Left, Bottom-Right: Corners with 50px margin
    Center: Perfectly centered in the current view

Opacity Presets:
Quick transparency settings:
    100%: Fully visible
    75%: Slightly transparent
    50%: Half transparent
    25%: Mostly transparent
    0%: Hidden (but still in list)

Workflow Tips
For 3D Modeling:

  Set display mode to "3D Viewport"
    Add orthographic reference images
    Position them at screen corners
    Adjust opacity to 50-75% so you can see through to your model
    Disable when not needed with the checkbox

  Open an Image Editor window
    Set display mode to "Image Editor"
    Add texture reference images
    Position them opposite your painting area
    Use lower opacity (25-50%) for subtle reference

For Comparison Work:
    Add multiple reference images
    Position them side-by-side
    Toggle visibility to compare different references
    Use opacity to blend references