How am I able to make that adjusted price for the future months

After creating a coupon code for a subscription fee, how am I able to make that the adjusted price for the future months (for the same person who signed up at the discounted rate)?

In the Coupon settings, you can apply the discount to the Subscription First Payment Cost. Please check the screencast below and give it a try.

Let us know if you need further help. Thank you!