To edit an announcement, simply navigate to the Manage Announcements screen, and either click the edit button for the announcement, or view the details of an announcement and click the edit button from the details screen.

This will bring up the announcement edit screen

Edit screen

You might notice that the Announcement Type only shows a single option. This is intentional. Announcement Type can only be changed when an announcement is created, after that those settings cannot be changed.

The rest of an announcement can be changed at any time.

When editing an existing announcement, we automatically reset all of the existing read receipts, so any user that has already seen this announcement will see it again with the changes you made.