The 'Announcement' tab under 'Communication' allows you to enter a notice that will be visible at the top of every page to some or all of the users logging into your instance. This can be used to post a very visible alert or reminder to your traders.
The 'Resources Pages' tab allows you to make an entire page of information available to your users. This can be used to provide supplementary information such as screen layouts, training material, software download links, etc.. You can create more than one of these pages if needed and restrict access to traders within a particular group.