Log into the Portal here: https://portal.neshealth.com if you're unsure of your password or have never logged in click the 'Click here to reset it' link, enter your email address then follow the instructions received by email (check your spam/junk folder if you haven't received it).
Once logged into the Portal click 'Resources' (at the top) then 'Download Scan Software', choose Windows/Mac as applicable and follow the steps shown.
Open BioSync using the desktop/start menu shortcut (Windows) or on a Mac you can find it in Finder->Applications.
Turn the miHealth on and connect it to the PC/Mac via USB cable.
Click miHealth Updater.
Select the desired miHealth language in the top-right.
Click Update, the language will be changed and any updates required will be downloaded at the same time so it may take a few minutes.