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 Meeting tool.
Click the arrow next to a meeting to expand the series.
Click the meeting's title.
Under the Agenda section, find the meeting item you want to edit. TIP: Use the Expand All button to quickly expand all items.