You can access your in-house bidder by using 2 types of accounts: an enterprise account and advertiser account.
Enterprise account features:
Creating and managing multiple advertisers
Setting up billing type and Price
Enterprise margin calculation across advertisers
Advertiser account
An Advertiser account is a sub account of an Enterprise account. this account type can run multiple apps. As an advertiser account admin you can create 3 types of users:
Analyst: This user type is restricted to using reports
Account manager: This user type can access reports as well as create/edit/run campaigns, but restricted from creating new users
Account admin: This user type has full access to Advertiser account features and can create new users
Create a new user
Watch the following video on how to create a new user under your Advertiser account