You have pledged to lend your aid and your adventuring skills to Durin's Folk and fight on their behalf in Mordor.
'I understand you know Gimli, son of Glóin? He has returned to Erebor after much time away, and is speaking with King Thorin.'
Thorin III, King under the Mountain, is at his throne in Erebor.
Gimli, son of Glóin, has come to Erebor to speak with the King under the Mountain.
Dwarves of Erebor that may wish to accompany Gimli to the Glittering Caves can be found throughout the Hall under the Mountain.
Gimli is near the provisioner in the Hall under the Mountain, arranging for the things he will need on his expedition.