Test Online Exchange for one user only

Our organisation currently is not using Microsoft Exchange Server.

I would like to try Online Exchange for myself without rolling it out to everyone straight away.

I have read the instructions here  :

http://community.office365.com/en-us/wikis/exchange/simple-domain-sharing-for-smtp-email-addresses.aspx

but Step 2 does not match anything I can see in Office365.  (Change the Domain Type from Hosted to Shared.)

I want to make sure that email is not disrupted for the organisation.

What do I need to do?

Thanks very much.