This article illustrates how to setup the My Account page as the primary tab in the customer portal.
Navigate to Setup

Navigate to Customer Portal | Settings

Choose the Client Portal

Customize Portal Tabs

Add My Account to Selected Tabs

- Highlight My Account in Available Tabs section
- Use ADD arrow to move to Selected Tabs tabs section
- Click SAVE
Verify How the Portal Looks

Verify by logging in as the contact to see how the portal looks to a client:
- Go back to the Contact.
- From the Work With Portal button
- Select Login As Portal User as shown in the screen shot here.