Each campaign in BoltMail can only be sent to one list and/or segment.
To send the same campaign to multiple lists or segments you will need to copy the campaign and change the List and/or Segment. Fortunately copying a campaign is easy, simply click the copy button found in the options column on the far right of the campaigns list (you may need to scroll the list to the right on smaller screens).
To prevent subscribers from receiving the same email twice make sure that you set the same send group for each of the campaigns. You can learn more about send groups here
In earlier releases of BoltMail 2 we did allow sending to multiple lists but this actually generated a merged copy of all the lists which was very slow and made managing your lists and unsubscribes more difficult, send groups is much faster, more powerful and replaces that feature. However you could mimic this behaviour by merging the lists yourself and then sending to the merged list. Learn how to merge lists here