Upload the plugin contents into your WordPress installation's plugin directory
The plugin's .php files and readme.txt should be installed in the 'wp-content/plugins/auto-post-images-api/' directory
From the Plugin Management page, activate the "Auto Post Images (API)" plugin
Edit the plugin image/thumbnail directory path and url in the Plugin Admin Panel to a directory outside the plugin inatallation directory. Note: If you use the default image directory inside the plugin installation directory you images might get deleted when upgrading
Copy the "imagecomingsoon.jpg" default image from the plugin directory ('wp-content/plugins/auto-post-images-api/images/')into your image directory. If you don't copy it then you will get 404 error for the image.
Upload images to the image directory and they will appear in the corresponding posts