How does secondary battery work

[Excited owner]

Hello,

On my CGT MY 2004, I am trying to work out how the secondary battery works.

So if you have an issue with the main battery,

1. Put the key in the ignition and turn the key left and then keep it turned left so that it will start or

2. Do you put the key in ignition, turn left once and then right and start as normal?

Thanks

[ColourRestorer]

Everything you need to know is here:
https://procarmanuals.com/vag-ssp-272-phaeton-onbo...

[Excited owner]

Thank you.

My goodness it is very complex indeed, one for my bedtime readibg.