if you are using the flowchart method, you can use the Flow Decision activity. So basically, you will check whether the first task is successful or not first, and add the Flow Decision activity below that, check for the condition, and you can decide if success, what to do, and if not, what to do…
If you are using the sequence method, you can use the IF activity to check the same condition.
Or else, add a Try Catch block, check the first task there, and based on the status, if its an error, do some exception throwing and stop the process, else you can continue the workflow…
Hope it helps!!