First I want to select the NPC like in the picture, and then click the first button. I chose to interact with the goal in the task mode, then what should I do? Sorry i'm a newbie

i got npcs ID, But this npc useless task is to send npc. In the first step, I want to select the right button of the NPC, and then select the first button in the dialog box.

take a look here: https://wrobot.eu/forums/topic/10723-quest-profile-code-snippets-part-3-updated-72819/

Use the search for "gossip" and you will find many useful code snippets for interact with NPC´s like 

Usefuls.SelectGossipOption(1);