The Create Call Task block creates an Outbound Call task in the queue for an agent to handle.
You must first create the Call campaign from the campaign builder. Then, once you've selected the Create Call Task block in the journey builder, you'll see a dropdown of call campaigns to choose from.
Call Campaigns Must Be in Ready State to Send
A Call campaign must be Saved as Ready in order to trigger it through a journey. If it is in Draft state, the call task will not be created and the next block in the journey will be processed.