After you have purchased Barcode Zone from appexchange, you can install the software.
Install Barcode Zone for Salesforce, copy sample Barcode Zone packages into your organization, and begin generating customized barcodes.
Use this procedure to install or upgrade Barcode Zone and confirm the installation..
When you click the above link it will take you to this page , then click on the Get it Now button.
Confirm your installation
You should see a package named BarcodeZone listed with any other packages you may have installed.