This is really the crux of marketing and promotions! You should be sharing your Bookshop link on social media for starters. But the key here is to get creative! There's no one-size-fits all plan for marketing; you've got to stand out! You could create a coupon and offer that as an incentive, or look into creating a book trailer. How about a press release? Influencers, you should offer free copies, too!
And of course, you should check out BookBaby's options for running ads!