There are two ways of integrating your Vanilla forum to your website: customize the theme so that it looks like your website and point a sub-domain at it or embed it into a page on your website. (Like this.) Embedding your forums has the advantage of integrating your community forum with minimal theming effort but there are a couple drawbacks:
1. Page load time
While Google tries to index iframed content, it doesn't always get it right. When the forum is on a sub-domain and linked to your website navigation, Google will have no problems finding a crawling the content. What's more, it's easier for people to create external links to specific pages on your forum. These links will help your SEO.
If you've weighed the pros and cons and decide to go the embed route, here is a short checklist to follow:
- Choose the embed friendly theme. This theme has minimal padding around it and will look good at any width.
- Ensure you have enabled embed in your dashboard.
- Set up the forum on a sub-domain. (Even though nobody will see the URL, this helps search engines attribute the SEO juice to your main domain.)
- Register this sub-domain in your Google Webmaster Tools account. (If you are not embedding, you should do this too.)