how to update .htaccess file of wordpress

Guys i am using wordpress.I would like to use nice permalink such as psyphil.com/postname.I hav set permalink to /%postname%/ under options tab,but posts are not visible under their own post name.i.e when i click to view posts in separate page i am stuck with 404 error.

I’m using windows server,cant i use nice permalink option with windows.

and how can i update .htaccess file.What should i fill inside it