Every chat, whether it's a 1:1 personal chat, or a big group chat, has the option to enable task creation. To enable tasks in a chat, click or tap on the "Tasks" button in the top right hand corner, then on "Enable". 

If you don't need tasks in that particular chat, you can click or tap on "I don't need tasks in this chat". You can always reverse this from the chat settings. To do so, open the settings, click on "Tasks" then click on "Show again" to make the task button appear again in the chat then tap or click on "Enable".