Encrypt the Request payload before post api request . where to add these (encryption)methods

I have locally created swagger editor then generated json , with the help of which created a swagger ui , easily able to do post and get operation , but this was plain json post and get , now i want to implement encryption for the data that i post and decrypt the data which is received as response where do i need to implement these methods (encryption and decryption methods)that encrpt and do post operation and decrypt and give data, and need to generate app_key , where to add these methods in editor or in UI ??