check the notice board in the Room of Requirement. You'll have to look all over the castle for the members. Once you have found the members, some will go to the room, some will require you to perform some sort of task to allow them to have time to attend the DA meeting.
You go back to the Room of Requirement and hold the DA meeting.
There was no password to get into the Room of Requirement, the members of the DA only had to walk past three times thinking the form that they wanted the room to take, and they got in.
The Room of Requirement.
In the room of requirement 7th floor
The Room of Requirement. Hogwarts provides the room when a student is in need of it. Hence why it is the Room of REQUIREMENT.
The Room of Requirement wasn't destroyed, it had a whole blew in the wall, so Umbridge could see in. All of the D.A. members could be found in detention with Umbridge, after she kicked Dumbedore out of his Headmaster position for creating his own army, even though it was Harry's idea, and the Headmaster had no idea.
They were in the room of requirement after a DA meeting.
They are waiting for you in the Room of Requirement on the 7th floor. Those you still have to find are listed on the bulletin board. Ask Nearly Headless Nick to show you where the other members are if they are missing.
Have you solved the challenges for them ? You need to solve all challenges then they will enter the room. when all 28 members are in the room you go in.
Go to the requirement room
Look on the Marauder's Map
Dobby the house-elf told Harry Potter about it and said it was the perfect place for Harry Potter to teach Defense Against the Dark Arts to the DA group (Dumbledore's Army).