You set up your account here:
https://rewards.nationals.com/login/LoginNationals.aspx?ReturnUrl=%2fmy-account%2fDefault.aspxThat site is basically a pass through and there will be links on the left hand side that redirect you to a Nats Ticket page were you buy tickets, RSVP, exchange tickets etc. You should be able to set everything up now. I signed up for 2018 season tickets and did the 2017 play off through here, winterfest, etc. Nothing loaded for 2018 yet. I have to Google how to actually set up the accounts, link then etc.
