If you want to fix your announcement message on the top of the Topic for everyone to see, refer to the following.
Hover your mouse over the message that you want to set as an announcement.
You will see the [...] icon to the right side of the message. Click the [...] icon and select [Announce]
Please keep in mind that only text messages can be set as the announcement. Comments cannot be set as the announcement.
3. Once the message has been announced, you will see the message fixed on the
top of the Topic for everyone to see.
Manage your announcements by using the hide/fold/delete features.
Although there is already an announcement for the Topic, anyone else in the topic can choose a different message to announce.