If you backed at one of the "pack" tiers or selected Aberrant Reflections or The Seers Sanctum as an add-on, you should have received the digital copy through an e-mail from drivethrurpg.

If you don't see the e-mail, check your spam folder or try logging in to drivethrurpg. They usually have account notifications with a link to the listing. Let me know if you have any issues and I'll make sure you get what you need.