There are two ways to apply a paragraph style:
- select it from the style drop-down menu list at left in the toolbar
- double-click on its name in the style sidepane
As the name implies, a paragraph style will be applied to the whole paragraph in which the cursor is (or the paragraphs over which the selection extends).
In case, you want a style applied only to a selection, you must create a character style. Character styles are not listed in the paragraph style drop-down menu in the toolbar (well a character style is not a paragraph style). Character styles are listed in the style sidepane after clicking on the second icon from the left in the pane toolbar. You apply them with a double-click on the name.
Read the Writer Guide about the various style categories.
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