When your organization has multiple Azure Subscriptions and you are entitled to work with them, selecting the correct subscription becomes an important thing to do.
Different approaches exist. I will have a look at the two most straight forward ones.
Using an argument to Connect-AzAccount
Connect-AzAccount holds specific attributes than can help you, namely SubscriptionName or SubscriptionId. If you know the Subscription name you want to connect to, issuing the following command directly connects to the correct subscription, after which you can start scripting: