How to unsubscribe after I has paid?

How do I unsubscribe an app, I tried for free, but didn't notice to unsubscribe. I was charged for a whole year, but I don't use the app?

On three or four times I have forgotten to unsubscribe and it is a heavy cost to pay for the whole year and I have already paid more than $ dollars for an app I don't use; As You can read her:

SubscriptionUnlimited accessAppEnlight Videoleap Video EditorContent ProviderLightricks Ltd.Date of Purchase26 December 2018Introductory OfferFree for 3 daysSubscription PriceUSD 44.63/year starting 29 December 2018Payment MethodVisa .... 2403You won’t be charged for the free trial. After the free trial ends, your subscription will renew at USD 44.63 unless cancelled by 28 December 2018.