The My Customers page is a mobile version of the My Customers vineyard tool. It lists companies (and their subsidiaries) you have added to the page.
Tap a customer company to open its employees and then tap any person to open its contact data.
Using this contact page you can call the person or send an email.
If you want to add a new company then tap 
and create a new company. It will be
automatically added to My Customers.