You can have 1 person assigned to a task and multiple people assisting.
Task Flow View
Drag and drop more than one profile picture on the task. The task will be assigned to the first person. Everyone else will be assisting on this task.
Task List View or from the Task Window
Click on a Task name to see the Task details. Click Assist and choose who you want to assist on the task. As you select the teammates, a checkmark will appear beside their name. Click Done.
Each person assisting will receive an email.
Watch how to add teammates to help you on tasks