reserved seat on shinkansen Tokyo to Kyoto?

I do not want to include a hotel package or the JR pass. The E voucher from Japanican only lets you select un reserved seats. I will be traveling to Kyoto on Oct 11, 2017.

Maybe I'm missing the context of your question, if so I apologize, but are you asking how do I buy a Shinkansen ticket for a trip from Tokyo to Kyoto traveling on October 11th?

Are you wanting to buy this ticket from within Japan or overseas?
The Shinkansen you want to travel on is the Tokaido Shinkansen, and there are three different named trains, Kodama which stops all stations and is slowest, Hikari stops some minor stations and all major ones, and Nozumi which is fastest and only stops at major stations.
You can buy the tickets on arriving in Japan at most JR ticket offices situated in JR stations (midori-no-madoguchi) or Travel Service Centers. You can pay with either cash or credit cards. As well there are ticket vending machines. When you land at your airport you can buy at a Travel Service Center. Familiarize yourself online at jreast.co.jp/e/ticket/purchase.html. and also check the timetable so you know what time you wish to travel. The ticket will have car number and seat number. You don't need a JR Rail Pass, its just like buying any train ticket for a reserved seat.

Since you mentioned Japanican, that means you've bought a travel plan voucher rather than a straight ticket, so I doubt you can change it to allow reserving a seat. But if you are going fromTokyo to Kyoto, since the train starts from Tokyo, you can go to the stationabit early and queue up to secure a seat, no problem.