Upload the folder ˇ°wp-post-iconˇ± into your ˇ°wp-content/pluginsˇ±
Log in to Wordpress Administration area, choose ˇ°Pluginsˇ± from the main menu, find ˇ°WP Post Iconˇ±, and click the ˇ°Activateˇ± button
Choose ˇ°Options->WP Post Iconˇ± from the main menu and start uploading your images or icons. Then when you are writing a new post, you could select which image to display on the right side option bar.