I was assuming that you were needing the address that is on file in the users record for that customer. If you are only planning on using the values for that order then you should be fine to just make use of the existing recordset on the page. This should have the bindings that you will need in your email message, you can just drag and drop them where you need them.
Just FYI if you did want to put in any info that is only in the users table it would be a standard Dreamweaver recordset that you would use. You would just need to make sure that you fill out the section for the filter part so that it is filtered for the user that placed the order. You would select the userID column to filter by, then specify an entered value and use the recordset value for the userID from the orders recordset. This new recordset would hold the details of the user that made the order. You could then make use of the values for that user the same as you do for the order by using the bindings that are available.
Please post back if you have any further questions or need any more specific information about any part of this I would be glad to help you.