#1 - July 31, 2014, 10:59 p.m.
Once the zone is open, Nexus-Lord Donjon Rade (in Stormwind, Orgrimmar, Shattrath, Dalaran, Vale Shrines, or your garrison) will have a chat option to teleport you into the Foundry. Assemble your group, set the raid difficulty to Heroic, and then use that option to enter. Take the back-right passageway from the entrance, and then take the first right to find the boss.
In your posts, please note your group size and makeup (high-end guild group, PUG, multi-guild team, etc.). Uploading and linking to a log parse at Warcraft Logs, or any similar site that can handle 6.0 logs, would also be quite helpful.