How to make an AWS process like API?

I am work on a project like an e-mail automation. I need to send email, get read or not read information of that mail, get the information of how many times click on link if email has a link and get the region information of the user. I looked at SNS and SES to send and get email information and I understand how to do basically. And after that I can watch these on CloudWatch. But I need to make this process on API. I searched on internet maybe I can use postman etc. But the credentials made me confused. This will be a basic application so how can I make an API like this, how can I trigger this send email? Any advice appreciated. Thanks in advance.