Hi Robyn, here is a video on how to reserve seating. You can also have the JR staff at any JR office so it for you free of charge if you find it more easy.

https://youtu.be/khpeDd5LDjU?si=uyikX8lpsp0IQphJ

Thank you!  Since I’m not near a JR station, is there another way to reserve seats?  I’m trying to go from Odawara to Kyoto on March 6th, on the Kodaua to Shin Osaka leaving at 1035.

Seating has to be booked via a shinkansen ticket machine or by any JR staff if the pass has been bought from Getjrpass.com I’m affraid.

It’s very rare to see full trains however, there’s probably no problem at all to reserve seating quick once you reach Odawara.