If you've enabled comments for a meeting, the comment box will appear below the meeting wherever the meeting is published (e.g. visible on your project page) during the specified time frame.
Here's what that looks like on a live project page:
If you're expecting to see a public comment box on your meeting but don't, double check the meeting comments timeframe.
For example, if you choose to begin collecting questions Starting two days before the meeting/event, the comment box for questions would not appear until 2 days before the meetings official start time.
You can update this setting at any time, and if you'd like to stop collecting questions after your meeting, you can update comments to "Don't Accept Questions" after your meeting has ended. All comments will be collected and can be sorted by meeting on the Comments tab.