This is where I come in

[frindle2]

Hello. Would you please explain the underlined sentence?
I think it means "That's why I wrote this book." Am I right?
Thank you.

-----from Le Road Trip by Vivian Swift
Travel. Yes, we all do it. But some of us do it better than others.
This is where I come in.
I wouldn't call myself a travel expert, but that's just me being modest.
OF COURSE I'm a travel expert.

 

[Charlie Bernstein]

It's an idiom. It means: This is where my skills are needed, this is when I'm needed."