Adding license keys from Command Line

I am using SoapUI Pro 5.1.2. I do not have UI on the CentOS machine where I have installed the SoapUI Pro 5.1.2. I need to add the license keys to use the SoapUI Pro 5.1.2. I need proper steps for adding the license keys for SoapUI Pro 5.1.2 from the command line interface (I don’t have UI to add the license keys). Can someone kindly help me in solving this issue as I need this urgently.