haibike chainring mod

I've had my haibike suduro hardnine 4 for about 4 years, and I've come to the point where I need to replace the chainring. I'm debating if I should try replacing the old chainring with a larger one like 42t, because I use my bike as a big commuter. The review states that you can add a chainring, so how can I add an additional chainring and front derailleur so I can also keep the torque that the 38t chainring holds.