update readme

Author: marcantondahmen

README.md

@@ -5,3 +5,12 @@ This repository provides a small, curated collection of size-optimized images us
 The repository also includes a script to fetch images from a specified Unsplash collection, resize and convert them, and generate metadata and a contact sheet.
 
 Processed images are stored in the images directory and committed to the repository. On push, the site is automatically built and deployed, exposing the assets via a CDN endpoint.
+
+## Adding Images
+
+In order to add images, follow these steps:
+
+1. Create a `.env` file based on the `.env.example` file
+2. Update the configured collection on [Unsplash](https://unsplash.com)
+3. Run `bash fetch.sh`
+4. Commit and push the added images