You can click on the wrench icon (if you are the admin) the choose Pin Topic
Then you can choose to pin this in a specific category (pin topic), or at the top of Latest (pin globally) across the whole community. Alternatively you can make this a Banner Topic for it to appear above the title space across the site until the user has closed it.
If you search for these terms on this site you will find more advice and best practice, particularly for Banner Topics