You can easily add an Announcement to your system that will be seen by all employees when they log into the system. Only admin level users can add control panel announcements. You can set system announcements to be 'required reading', where all employees must acknowledge they read the message as well.
Enter your announcement and click Save. The announcement will now be visible by all employees of your organization their control panel when they log in. To Add 'Required Reading', enter your message. Check the box 'Required Reading' and click save.
Now, when an employee logs in; they will be presented with the message and must Acknowledge that they've read the message.
Once they click they've acknowledged the message, a system log entry is made.