User account does not have access to App Annie Intelligence API

When I tried to use below App Annie Intelligence API

https://api.appannie.com/v1.3/intelligence/apps/ios/market_size?data_break_down=country&categories=Overall&device=iphone&granularity=monthly&start_date=2018-01-01

I got below 403 forbidden error.

{
    "code": 403,
    "error": "This user account does not have access to App Annie Intelligence API."
}

May I know how enable access for App Annie Intelligence API