You can edit your license number by going to the Employees page and selecting the technician you want to add a license number to.
Next, select "technician profile" in the nav bar on the right for that employees user profile.
Under "qualified to perform what services" you may select all of the service types that this employee is licensed to perform and then add the license number individually for each of those services.
If you click on the box and the License # field doesn't drop down, you need to go to settings->types->service types to check the "Requires License?" box under the service type.
