Hi, you have to download the latest installer from Adobe:
Tools > Report Builder
Check that you are downloading the correct version for your computer (32-bit Excel or 64-bit Excel - I would guess that most people would be on 64-bit now, but they may not be).
Close Excel completely and run the installer... you might need admin rights on your computer to do this (or contact your IT department to run it for you).
Check that the version did upgrade.
In Excel, you can see the version after logging into Report Builder by checking options (there is a greyed out "Update" here, that hasn't worked for some time)