When you create an announcement, rather than publish it immediately, you can save it as a draft.
As a draft, you can edit it, then when ready, you can publish it.
On the main menu click Announcements.
Click View drafts.
You then see a list of your current drafts. You can see the author, who it was last edited by, and the last time it was saved.
To edit or publish a draft, click on the pencil icon.
Click the rubbish bin icon to delete it.
Make your changes, then when finished, you can either save it as a draft again or click Publish to publish it to everyone.
📌TIP: If you want people to be notified about the announcement via email, ensure you select Notify employees before you publish it.