Always look on the Mikrotik website to find the latest procedure to update firmware on a Mikrotik device. As of this KB date, the procedure is to login to Winbox, connect to the correct router and click on “Quick Set” – see image below:
HERE IS A LINK TO THE SPECIFIC INSTRUCTIONS ON THE MIKROTIK WEBSITE: https://wiki.mikrotik.com/wiki/Manual:Upgrading_RouterOS