Hello, I'm going to buy my interrail global pass with Renfe.
After that, how can I do to book the different trains that I want? I have to do that in the renfe app or I have to do that in this rail planner app?
If it's the second one, will I need the code of my interrail pass or what things will I need?
The rail planner app cannot book reservations. The Renfe app cannot do that either.
Since you seem to live in Spain, the best way for you to book Spanish reservations is at a Renfe ticket office or by phone.
Some Spanish reservations are available via on interrail.eu but they are more expensive than directly via Renfe.
For other reservations, see this thread:
and this page:
https://www.seat61.com/interrail-and-eurail-reservations.htm
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