If you want to use a custom system using the Microsoft Translator Text API, it requires deployment on Microsoft Translator servers, so that the Translator Text API can find your custom system. Deployment requires a subscription to the Microsoft Translator Text API on https://portal.azure.com. The minimum required Microsoft Translator Text API subscription for deployment is "S1 (Pay As You Go)". See the Microsoft Translator subscription tiers listed in the Cognitive Services Pricing webpage.
If you do not have an Azure account, you can create one on www.azure.com. Every new subscriber who signs up for the Azure Free Trial receives a USD $200 credit, or equivalent in your local currency. This is a 30-day trial subscription to Azure, and not to the Microsoft Translator Text API. More information about the Azure Free Trial is at www.azure.com. When the Azure Free Trial ends, you need to continue a subscription to Azure to be able to use the Translator Text API. You can sign up for the Pay As You Go subscription to Azure, you will be charged only if you use Azure. Learn more in the Azure Free Account FAQ.