When a software update is available, your Touch will automatically start downloading it the next time it syncs with the app.
Your Touch will need enough battery to complete the update, so it's always a good idea to have your Touch plugged into the charging cradle before you attempt the update.
Make sure your phone/tablet is connected to a reliable internet connection when attempting to update the Touch.
If your update is having trouble completing, it is possible that your Touch has some stray files saved on it, causing the update to stall. But not to worry! There are a few things you can do to reformat your Touch to successfully accept the update.
First, force quit the app and do a factory reset on your Touch (instructions below). Make sure you have synced your current steps with the app, otherwise you will lose your current progress. You will then need to re-pair your device with the app. Once you do that, you should see the update prompt.