If you mean the UPDSendReceiveString example, the code for sending a packet resides at the end of loop(), commented as "send a reply...". You have to fill the ReplyBuffer with the information you want to transmit, before you invoke these 3 lines of code.
Put these lines into a function, and call that function whenever you want to send the content of ReplyBuffer. Or pass to the function the buffer containing the text to send.