1. Navigate to Settings > Integrations> CArrier Setup
2. Click Add New and choose 'USPS Stamps.com'
3. Enter in your Username and Password
4. Click ‘Save’
Other Tips for Setting up your USPS Stamps.com Account
Note Usage: Choose to include the shipment number or SKU number in the 'Note' field.
Click the ‘Options’ tab to set default settings for your USPS Stamps.com account such as default package type, default confirmation, default box dimensions and description