Parallel Branching has one input route and multiple output routes, it will run all routes (branches) in parallel.
After selecting the "Parallel Branching" item from the "Add Flow Control" menu, you will see the editor like this:
Here you can specify how many branches you will need. You can append more branches later, by double-clicking the item in the behavior editor.
Here is an example of how to define parallel tasks by using the Parallel Branching:
Here is a working example on ForeUI store. You can download it and learn how to use Parallel Branching from it.