Hello
I mean : "first IG account" is the first account created when I opened the account with IG
I use it here
https://www.ig.com/it/login
to enter in the private area of the web site

Then I created API Key and (both for real and demo account)

Later
Following the istruction here "http://labs.ig.com/gettingstarted"

Getting started
To begin using our API all you need to do is:
Create an account
Generate your API key
Start coding

I create a new account (I mean , ID and passowrd) to use
in this link
http://labs.ig.com/sample-apps/api-companion/index.html
Buy this second account has only this functionality to check API request like to find the IG'S symbol of EUR/USD