The video shows how to add site to existing task.
Tasks
Select the task
Edit
Select sites
Add Item
Active filter by meter type
Ctrl + A (select all)
OK
Save and close the task
Task - Add Site To Task
Choose navigation item Task
Select Task to add new meters
Select Edit
Select Sites
Use Add Item
In table of meters is possible to use filters
CTRL + A to select all records
Task - Add Site to Task