Hi Rosa
For Identical vouchers, although you are required to give Form for Email, you may not necessarily attach a TG. After execution you may search the vouchers in Web UI - Marketing - Search Vouchers.
For Unique vouchers where you are required to have a TG, you may try extracting them using the "Open Channel" data File export to have them attached to the campaign. Please refer best practices for more info on this channel.
Hope this helps.
-Raj