How to upgrade from Thunderbird 78.5.1 to Thunderbird 78.6?

I've installed TB 78.5.1 (by adding the relevant repository and performing

Code:sudo apt-get update
sudo apt-get upgrade(I moved from the main TB channel to get support for MFA.)

This works fine.

I see that 78.6 is now available.

I've downloaded from https://www.thunderbird.net/en-US/.

But I'm not clear how to upgrade.

Any advice gratefully received.