Odakyu Sightseeing Service Centre in Shinjuku

1) How do I walk from Narita Express Platform 5/6 in Shinjuku Station to Odakyu Sightseeing Service Centre West Exit?

2) Is the Odakyu Line gate to board train right next to Odakyu Sightseeing Service Centre?

3) How do I walk from Odakyu Sightseeing Service Centre to Shinjuku Washington Hotel?

Thank you so much!

Both JR East and the Washington hotel have access maps on their websites. A simple google search will find them.

hakata14, you are not helpful, at all! I think you would better not post instead of writing unhelpful responses. Or at least you could link to the page you mentioned. Not everybody is as Japan-travel-internet-savvy as you seem to be.

1) How do I walk from Narita Express Platform 5/6 in Shinjuku Station to Odakyu Sightseeing Service Centre West Exit?

If you are arriving at platform 5/6, it is best to go to the very front of the platform (towards the South Exit) down the stairs into the underworld and follow the signs for "Central West Gate" or "West Gate":
http://www.jreast.co.jp/e/stations/img/map_e/e866.pdf

Once you pass through either gate, the Odakyu service center is then just up the stairs:
https://www.odakyu.jp/english/support/center/

2) Is the Odakyu Line gate to board train right next to Odakyu Sightseeing Service Centre?

Yes, some of the ticket gates are close the the service center.

3) How do I walk from Odakyu Sightseeing Service Centre to Shinjuku Washington Hotel?

There are ample of bilingual maps in the station that show you the way. You have the option to go everything underground or above ground. As a first-time visitor, I personally would probably prefer above-ground unless it is raining. In addition, Google Maps provide an amazing amount of details for today's travelers:
https://goo.gl/maps/TXAhrpGHmWp

Did you use google to create the map?