I need to display the latest date of donation with the corresponding amount from the child object to the parent object .Appricate the help!

In my DE there is no action in the list named Assign Task Action where as the challenge says that The rule should fire an Assign Task action.PLease help!!

Hello everyone, I just get started with Salesforce development. Is there a possibility that the total amount can show up on the page I post. I want to get the sum of the Amount and display the number on this page. 

I need to display the latest date of donation with the corresponding amount from the child object to the parent object .Appricate the help!