Hello
There are two options that are available to you.
1.) Employ a seo expert and have them promote your site for you. This can be expensive!
2.) You could have ago at promoting your website yourself.
There are many ways of doing this.
Here are a few ideas.
Write an article about your website theme then submit it to article directories.
Submit your site to free directories.
Get reciprocal links with websites of the same theme as yours.
Create a blog to promote your site.
Design a website template with your site link in the footer and submit that to template directories.
The good old word of mouth. Tell your friends and family and ask them to tell there friends and family.
To help you with SEO and promotion there is a forum dedicated to this and it is a great forum to sign up with and to get help and advice.
http://forums.digitalpoint.com
I hope this post has been of some help and good luck with your site promotion
Webby2008