Each of the participating authors in each newsletter cross-promotion event receives promotional material to add the giveaway to their newsletter. They spread the word through their newsletter list and also through social media postings which are then usually shared by reader participants, friends, etc.
Example of promotional material sent to participating authors to add to their newsletter
(not linked now, but linked during the promotion)
Win up to NINE Cozy Mystery eBooks!
(2) Grand Prize Kindle "Gift Baskets" of ALL NINE COZY MYSTERIES!
(9) Winners of Individual Books (randomly selected titles)
Plus a special bonus chance to win!
Example of the Giveaway Page readers will visit to enter the giveaway