Link to the form: https://bullart.com/ig-birthday-winners/
When you send a DM (direct message) to Instagram winners, you can say something along the lines of:
It was really special to see your post!
Please go here to claim your prize:
https://bullart.com/ig-birthday-winners/
I will mail you [details of the prize].
[If needed, instruct the person to make a selection or indicate a preference in the Comments field.]
Thank you again so much for your post. It really made my day!