Battle Net, is basically the same as the old account management.

Log into your B.Net account, go to the account you want to refer from.
Send the RAF invite email.

Use the email to create the account.
Upgrade to a retail version with a battlechest or vanilla wow.
Link the account to your existing B.Net account (this assumes you are keeping all 4 new accounts, for a total of 5).
Go to the new accounts management (should be a drop down box) within the B.Net.
Send the RAF invite out the same way, this time from B...

If you are keeping all of the accounts, then you can have them on the same B.Net if you like.
The advantage of this, is much easier account management.
There are rumors that bound to account items, might eventually be bound to B.Net items.

You can also do one B.Net per account, or five B.Net accounts in total.
If you are using an authenticator to protect your accounts, then one code can simultaneously get all the games into wow.
In this case, the links are the same as before, just invite the new account to its own B.Net rather then the B.Net of the first account.