Well you can just format the text so that it appears the way that you want it to look. That will be what is referred to in InDesign as a local override. You'll see a plus sign next to the name of the style. If you're asking how to modify the style so that all text with that style applied updates, then you can right click on the name of the style and modify the attributes on the left hand side to adjust the appearance to your liking. If you turn on preview in the Style Options dialog box, you can see the changes in the document as you make them. Click OK and you're done. You can also modify one instance of the text in the document that uses the style, then right click on the style and choose "Redefine Style".
You should always work with correct styles without manual overrides. It is essential for a lot of functions. You can always redefine styles or create your own.