Note: you must be on Sendspark Pro or a higher plan to use Video CTAs.
Follow these steps to add a "Text Me" button to your videos:
Toggle on the Call-to-Action field
Write your desired button text (ex: Text Me)
Write sms: and your phone number where it says URL (ex: sms:1234567890)
You'll be able to check that everything looks good in the preview area on the right of your page 👍