Yeah that quote is so broad and confusing af lol no you shouldn't just do nothing and wait for a girl to fall from the sky.
I think what it means is to be open minded to possibilities. Invest in yourself, learn new hobbies and meet new people to actually get to know them, not only to "date". By making new friends and branching out you will increase the possibility of meeting someone you are interested in dating, and then you can make a move.
Be open to get to know people that are different from yourself as well. When I first met my husband I thought he wasn't the typical guy I would go for, but I told myself hey maybe my usual type is shit so I should be open to hanging out with someone different. Fast forward a few years later and now we are happily married. So I think that would be my best example/interpretation of "it'll happen when you least expect it".