Navigating to a random target point

how do you do that? I tried “Get All Actors of Class”, it returns an array, but I can’t get the array’s length or element. The error: Default value ‘’ for TargetArray is invalid: ‘Literal values are not allowed for array parameters. Use a Make Array node instead’

[EDIT]
The problem was execution flow: the “Get All Actors of Class” wasn’t executed at all. The second graph is corrected