You can have 1 person assigned to a task and multiple people assisting on a task.
Task Flow View
From the Tasks page, on the right click Quick Assign.
Select the person’s photo and drag it onto the task. The first person you drop on the task will be assigned the task. Anyone else you add will be assisting.
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 if they have notifications turned on.
Watch how to add teammates to help you on tasks