There are many different ways, but I can share with you two methods I have used.
First method is the easiest, write from your personal experience. I went to kpop concerts before, so it was easy for me to write. If you haven't been to one, it's a bit of a culture shock. That in itself is interesting to write and read about.
Second, think about the bonding moments of your characters. They might both enjoy the concert and bond over shared interest. Or, they could have an entirely different experience, but learn to appreciate each other differences.
I wrote 2-3 chapters with the characters going on a date at a Cpop concert. It was fun.