Chocolatey should automatically set this repository when you have a valid license. In case it doesn't, refer to your chocolatey.license.xml and find the Id attribute.

Now use that license Id to replace '{licenseId}' in the following command:

choco source add -n chocolatey.licensed -s https://licensedpackages.chocolatey.org/api/v2/ -u customer -p {licenseId} --priority 10

While you are able to search this package repository without a license id, you are not able to install any packages without a valid license id.