You can do it by hand. It's in the owners manual. Hit PGM while in the trunking then T then arrow up or down to the ID of the talk group press text use the number keys to enter the name
Go into program mode in the desired bank; and press FUNC TRUNK. Use the UP and DOWN arrows to navigate to each TG ID. To enter text for an ID, press TEXT, type the text (2 keys per letter) and press ENTER. Do that for each TG.
Note: during scanning, when the scanner stops on a conversation, if you see the TG ID instead of the text, press TEXT during the conversation.