This is a classical tealight heated burner, you will place your wax melt into the dished area and then heat from below with a lit tea light.
NOTE: Unlike a candle, the wax in a wax melt doesn’t disappear as you use it. Instead, eventually, the wax will lose its scent. When this happens, you will want to remove the wax from the burner to change it over to a fresh new wax melt.