Open the email in question, and in the header click on the name of the sender in the From field. That will open a dialogue box, and in the upper left corner you will see "Add to address book".
Thank you -- that works for one address at a time -- I would also like to copy and paste a group of addresses into the address book -- that doesn't seem to work -- any solution?
The only way I know of to put multiple addresses for different contacts into the address book is to import them from a source that can be exported as a .csv or vCard file. So you would need to export them from the address book in some other email program.