It's easier done than said.

If you can modify the formatting of a paragraph or of text using Format - Paragraph or Format - Character, you can also modify a paragraph style, because that uses about the same dialog boxes that function in the same way. The only difference is that the dialog box for a paragraph style has more tabs.
Format a paragraph with bullets as you want it (I assume you can handle that), select it, then press F11 to open the styles list and click the top right button in that list, with the green "+ mark", select
New from selection to define a new paragraph style based on the formatting of the selection. A dialog box opens that allows you to enter a name for the style and to tell to what "parent" style it should be linked. For that, use the style used for the main text of your document. Whenever you want to change the formatting of text with bullets, you have to modify the paragraph style that you just defined instead of invoking Format - paragraph or Format - Bullets and numbering.