Your first announcement may be used to welcome and orientate students to your course. 

Based on Minimum Presence in Blackboard, course sites (with at least a welcome message) should be made available to students as early as possible, and at least one week prior to the first teaching activity

Welcome message resources

Text Welcome message

To create a welcome message refer to the Add an Announcement guide. To hide links to course content that are not yet ready refer to the Course menu design guide.