You can edit announcements from the Communicate page.
Notes:
For details on how to access the Announcements channel, see View announcements.
If you previously "pinned" an announcement so it appeared at the top of the list of announcements, you can edit the announcement and unpin it so you can pin other announcements. When you unpin an announcement, it appears in chronological order in the announcement list.
You can edit only announcements that you create.
To edit announcements:
Select Communicate and click Unread Announcements.
From the list of announcements on the left, select the announcement you want to edit. The announcement appears on the right.