Multiple Domains to site being Indexed?

[greash]

Hello:

I have recently registered two extra domains that I want to point to my original site.

Here's my question, How do I set it up so that the other domains can be indexed as well, or is that only possible with the main domain?

I can either forward the new domains to the existing ones, or I can create a site for each of the new domains and have them redirect automatically to my exisiting site.

Any suggestions and/or advice would be appreciated. Thanks in advance.