If you ever need to update your already shared meeting poll, with FreeBusy add-on you can do that by following these steps.
You should have FreeBusy Chrome Extension or Outlook Add-on installed on your respective Gmail or Outlook accounts.
(These steps remain largely similar for Outlook and Gmail)
If meeting poll is part of your previous emails, Click on "Reply All" and make sure original thread where you have shared the meeting poll is part of the email body.
Turn on FreeBusy sidebar.
On Gmail Web
On Outlook Desktop App
On Outlook Web App
3. This will open the FreeBusy sidebar and load the meeting poll. There you can edit the meeting poll. Once you are done click on "UPDATE LINK".
Just to note : You will have to delete original snippet added by FreeBusy, since FreeBusy will add new updated snippet and links to meeting poll.
For Outlook on web, if meeting poll is part of previous emails, you have to make sure that you click on "..." icon and expand email thread which contains meeting poll in email body. This will help FreeBusy detect meeting poll.