This is a installation guide SEO URL for opencart 1.5.2.1
1. Upload file seo_url.php to your server in catalog folder - controller - common (replace the file if already exists).
2. Login to the your store administrator. Click menu system - settings - edit your store - click a server tab - In Use SEO URLs option select Yes and then click Save.
3. Please upload a file .htacces to your server in root folder (public_html or www).
4. Import file database.sql via phpmyadmin. If you use a table prefix, don’t forget to change the database.sql. Edit table prefix on the words url_alias (for example: store_url_alias).
5. Please check your store for example affiliates menu, accounts, etc
6. Edit your category or product via administrator. Click menu catalog - select a category / product - edit the selected category / product – click data tab - find SEO keyword and type your SEO Keyword.
Demo : http://opencart.pijaronline.com

Good Luck
M. Multazam, S.Kom
www.pijaronline.com (Opencart Indonesia)