Normally I would mark Your question as an Off Topic as it is hell clear You did not use GOOGLE before asking here... As there are many tutorials (and I believe also some similar questions regarding this here on SO).
- First of all You would have to go to Your OC and rename
htaccess.txt
file to just .htaccess
(yep, with the dot in the front)
- Second, go to Your administration -> System -> Settings -> click edit Your store and on tab Server (I guess) You'll find option Allow SEO friendly URLs (or something similar) - check the checkbox and hit on Save
- Now You can walk around the administration of categories, products, informations and manufacturers and all of these have an option SEO keyword (when editing/inserting one) - this field then is used for Your fancy SEO URLs...
Enjoy!