Hi,
In order to create email accounts, you will need to sign in to your Microsoft Office Live account with your Windows Live ID (primary email ID) which you have used during the registration of this account. I would suggest you to first delete cookies and temporary files from the computer because every time you log on to the internet; cookies are stored in your computer's cache. Visit the following link to know how to create email accounts:
http://office.microsoft.com/client/helppreview.aspx?AssetID=HA102262931033&QueryID=6D-F3AcnT0&respos=1&rt=2&ns=OFLV20&lcid=1033&pid=CH102262851033
If you are not getting the option to create email accounts associated with your custom domain then I would suggest you to visit http://who.is and confirm whether the domain is registered on your name successfully or not.
If the domain is successfully registered on your name and still you are not getting the option to create email accounts associated with domain then I would suggest you to contact Microsoft Office Live Support Team.
Note: You will not get the option to create email account associated with the domain if you have partially (website only) re-delegated your domain to Microsoft Office Live.