You'll need your API keys, so go to https://dispatch.shipday.com/dashboard#accountInfo if you don't have them.
You will get your api key from Shipday account. Go to Account Info, there you will find api key option. But to get api key visible you have to put your account password.
Think of your private key like a password:
Store it securely
Don't share it with anyone outside of your organization
Don't put it in any code on your website or in a Url that someone could find