How make a marketplace using coins

In my game I made a collector which shows the amount of coins collected during the gameplay. I would like to use those coins to allow the player to unlock new characters to play.
So what I need is a marketplace in the game which allows the player to buy new characters.

yeah pls i wanna know me too

This is quite an undertaking (that would take too much space here). I recommend watching this tutorial and also go through that entire series. It will set you up with the marketplace portion.

In terms of new characters, try this tutorial.