Go to Objects > Assign Modifications. Select the objects you want to assign. Choose the right Project and Press button Assign.
Now the objects are assigned to the project. To see all modifications on a project, press Modifications in the Project ribbon.
In the Modifications page you can set duration from a chosen point. You can use this when you want to know how long you have worked on a particular project. This can be used when you have to fill in your hour registration at the end of the day.