Admin' level permissions on the project's Meetings tool.
OR
'Read Only' level permissions or higher on the project's Meetings tool with the 'Manage Meeting Items' granular permission enabled on your permissions template.
Additional Information:
You can edit a meeting item at any time in either agenda or minutes mode.
Steps
Navigate to the project's Meetings tool.
Click the Meeting Title.
Under the Agenda section, click Edit next to the meeting item. Note: Alternatively, you can click any field with a blue caret.