Hello Kingsley,
Welcome to our forum and thanks for contacting us with your question!
Solutions suggested by my colleague sebastian.h are still viable, if you want to show all series in your legend then you should assign them with
showInLegend: true option. If you want to edit default legend labels then you should use
legend.labelFormatter callback. If you want to edit legend even further then you will most likely have to create your own custom legend, but it really depends on what exactly do you want to achieve. Please check these docs for all available options thoroughly:
https://api.highcharts.com/highcharts/legend.
I could tell some more specific solution but first I need you to provide me with simplified demo of your chart and more details about your expected results. You can start here:
https://jsfiddle.net/BlackLabel/g96kt8jo/
Regards!