If you want to visit Galaxy's Edge, aka Star Wars Land, at Disneyland during the first month it's open, you're going to need a reservation.
It's still unclear how you will be able to make reservations, but if you really want to ensure access, then you better stay on the resort. Disney says that guests staying on the resort during the above time period will receive a "designated reservation." Which we're guessing means that's your best bet to ensure you get in.
And remember, the DisneyLAND version will open first — DisneyWORLD's opening isn't slated until August 29. That's like a billion parsecs away!
May the Force, and some luck, be with you if you're planning on going for it at the Disneyland opening.