If the Announcement Editor is not already open, open it:
On the Announcements tab, expand the Announcement folder as necessary, and open the desired folder.
Open the Announcement Editor in one of the following ways:
To create an announcement, click Create Announcement.
To edit an announcement, check the box next to the announcement and click .
In the To box, specify the users and groups to which you want to send the announcement:
Type the names of the users and groups, using correct case, and separated by commas (,). Click Check Names to make sure that your entries correctly correspond to actual users or groups.
To select from a list of users and groups, click To. For more information, refer to Select Users and Groups.
To remove a user or group from the list, click next to the user or group name.
In the Subject box, type a brief description for the announcement. The subject displays to users under My Announcements and they must click the subject to view the text of the announcement, so make sure that the subject conveys what the announcement is about.
In the Announcement box, type the text of your announcement and format it as desired (for example, you can change the font or add hyperlinks or images).
In the Expiration
Date box, type the date on which you no longer want the announcement
to display to users, or click 
to select a date from a calendar.
If necessary, click Folder, to select a different folder in which to store this announcement.
When you are done, click Finish.