What is the correct way to link "activities" and "objects" in a UML activity diagram?

Question

UML

I am making a UML action diagram for a site where there is a sequence of filling out forms, and choices to go to the next form.

It is not entirely clear whether these forms should be inserted as objects (in a number of tutorials, objects are not inserted at all), and if inserted, where exactly? In the main thread, or just on the side, and to them the arrow from the action block.

How is it commonly done?

Thank you.