In order to use the API you will need to use the credentials which you can find in your account dashboard.
Your API Keys will appear in your API dashboard as soon as you have an account.
With each request to the API, make sure to include the API Keys in the headers of the request. The server expects two headers relating to authentication:
SB-API-KEY-ID: This is your API Key
SB-API-SECRET-KEY: This is your API Secret
It is generally best practice not to expose your API keys by using them from the frontend, and Sendblue actually disallows requests from frontend applications entirely to keep your keys safe