How do I use the Option Inspector to change options?

The “global” setting alters global options.

The “notebook” setting alters notebook options.

The “selection's style” setting alters the style options for the type of selected cell. (This is unavailable in Mathematica Version 4.0. You should edit the style sheet.)

http://support.wolfram.com/mathematica/interface/options/stylesheet.html

The “selection” setting alters the cell options if a cell bracket is selected and selection options if cell contents are selected.

Options will be greyed out if the given scope or current selection do not allow you to edit them.

Changing options with “selection's style” will only edit the notebook's private style sheet (it will create a private style sheet if one does not exist), not the shared style sheet.

http://support.wolfram.com/mathematica/interface/options/sharedvsprivate.html

Check boxes

Options that can only be set to True or False will have a check box which toggles between these two values.

Drop-down menus

Many options have drop-down menus that allow you to select from a set of values. Click the menu to activate it, and then select the option you want. Note, not all drop-down menus contain all possible values for an option. If you wish to choose a different value, you will need to edit the option manually (see below).

Dialogs

Some options have buttons which give access to a dialog box that allows you to change an option.

Marker

If an option is set for the currently selected scope, a marker will appear to the left of the option. To remove the option at the currently selected scope, click on the marker so that the marker disappears. The option will change to the value when no option is set for selected scope.

Manually

All options can be changed manually. Click on the option value and the value will become highlighted. Then use the keyboard to edit the option. Then press Return. If you do not press Return before selecting something else, the option will return to its original value.