Approved for Venture X! Now what?

Hey all! Super excited to be approved by this card!

Here is my concern: When I got the SavorOne card, I met the Welcome Bonus of spending $500 in the first 3 months. However, because I didnt opt-in(???), I didn't get the reward

For the Venture X, they offer 75,000 Miles (I believe thats equal to $750? Please let me know if I am wrong) when you spend $4,000 in the first 3 months.

I just want to know if you are aware of what I need to do to make sure I get that bonus. Thank you all so much!