Reservation Madrid - Barcelona. How to make?

Hi, my name is Sofía. I’m from Argentina.

Earlier today, I posted a topic asking about seat reservations. They provide me a very helpful guide, but I still couldn’t solve my problem. 

I’m trying to make a specific reservation for a train that goes from Madrid to Barcelona.  

This are my travel details:

• Departure date: 07-15-2022
• Departure time: 9:30 am
• Arrival time: 12:37 am
• Route: Madrid- Puerta de Atocha to Barcelona- Sants.

I’ll wait for your reply.

Thanks, 

Sofía.