Step 1: Navigate to All Jobs and select your Job
Step 2: Select Scheduled Tasks
Step 3: Under the Bulk Actions drop down select Assign To
Step 4: Tick which Tasks you wish to Assign then Next
You can also select Select All at the top to select all tasks, which is what we are doing in this example.
Step 5: Assign your User & select Done
You can tick to send a notification to the assigned user.
As you can see below, the selected user is now assigned to all the Jobs tasks.