The Disneyland resort has announced more details on reservation to visit Star Wars; Galaxy's Edge Opening Month:

Quote Originally Posted by Disney Parks & Resorts

If you are planning to visit Star Wars: Galaxy’s Edge at the Disneyland Resort between May 31 and June 23, 2019, a reservation and theme park admission are required. There is no additional cost to make a reservation, but reservations are subject to availability.

Specific details on how to make reservations will be available on Disneyland.com on May 2 at 8 a.m. PT. You must have a Disney Account to register for a reservation so be sure to create one before registration opens at 10 a.m. PT.

Guests looking to guarantee a reservation to Star Wars: Galaxy’s Edge today can get one by staying at a Disneyland Resort hotel between May 31 and June 23, 2019.

Guests staying at a Disneyland Resort hotel between May 31 and June 23, 2019 will receive a designated reservation to access Star Wars: Galaxy’s Edge during their stay. One reservation per registered Guest. Each Guest is required to have valid theme park admission. If the hotel reservation is cancelled, the Star Wars: Galaxy’s Edge reservation will be cancelled. Access to certain experiences in the land are subject to capacity and other factors.