Browse to System / System Updates and click Check for updates. The first update brings the system to the most recent version of the 4.7 branch, as of writing 4.7.06.
Once the system is upgraded, you should be able to Check for updates again and now 5.0 will be offered. Updating within major revision takes less time than between major versions. The update to HSMX 5.0 will logout the web management administrator.