We updated the download packages again today to solve this bug.

To upgrade, just upload the new files. There's no upgrade process.
Just a note to say we re-built the download packages last night due to a last minute bug. As such, in your customer area you will be looking for 2.0.6a

If you already upgraded, no further action is required. The bug, specifically, was related to errors on upgrading so if you completed the upgrade without any errors, there's nothing to worry about.