Hey there, @Winda_Lis!
Ryder here from the Social Care Team at Shopify. Thanks for posting! I'd be happy to explain the steps necessary in order to cancel this order.
In the lefthand menu of your Shopify Admin, you'll want to go to Orders and locate the order in question. At the top of the page, you'll see the "More actions" option. If you click that, it'll drop-down a menu where you can select "Cancel". This will void any uncaptured payments.
We have a guide on how to cancel and/or refund orders that you can reference, but I've also recorded a video with the steps which you can watch here. I hope this helps! Please let me know if there's anything I can clarify.