Train connections & reservations

I want to make a reservation with interrail and also one without for someone else not having  interrail to travel together. How can I do that?Thanx 

Hi everyone! I am quite new here and also in Eurail. What is the train I have to take from Rome to Naples? And... where it is located?

Hey I have a question. When I travel on trains where reservations are not obligatory, do I just have to get on and show the Interrail ticket on my mobile phone? Or do I have to buy a 0 Euro ticket somehow beforehand?

HelloI want to travel to Spain this summer. I took a Global Interail Pass.I am unable to book seats on domestic lines:barcelona -valencevalence -madridmadrid - barcelonaeven on the smartphone application.Maybe there is no need to make a reservation, but then does that mean I can travel free of charge and just with the pass?Do you know of a help number that I can reach?Thank you all for your help 

What is the least expensive method of making a train reservation?

Hi! This summer me and my friends are going to Italy, we already have our interrail pass ‘one country-italy’ but we can’t find if the pass includes a ferry in amalfi coast to capri. Anybody knows? I’m sorry for mt english 😅 

I am currently planning my trips and would like to know which trains require extra seat reservations.