To interact with an object and access its properties, it must first be selected. Objects can be selected by clicking on them in the viewport. Multiple objects can be selected by dragging a selection box over top. Objects can be added to the selection set with Ctrl + click and removed with Alt + click.
The Selection Panel provides a number of different tools that change automatically when objects are selected.
Move, Rotate and Scale allow you to both select and manipulate objects. More information on these is provided on the Transforming Manipulators page.