Building upon Brad's response.
For styling in a dynamic block. Your block should contain HTML tags such as DIV, STYLE, P, etc.. Each of these tags can be styled with CSS using ID's or Classes. For instance:
<div id="list1" class="list>
<div id="row1" class="listContent">
.... row content
</div>
</div>
With this information in a dynamic block, you can style it with css in a CMS Stylesheet. Stylesheets are related to a Theme. Here is a screenshot of a stylesheet for one of my sites.
I put all my CSS for my site in the Site Overrides Stylesheet. Notice that it's order is 9999. This will come last in all the Stylesheets.
You can then add the appropriate CSS. Remember the more specific you are in the CSS selector the higher the precedence.
div.list {
}
div .listContent {
}
These selectors would apply the CSS styles to the list and listContent classes in your block.
For this CSS to be on the page, then the page must be using the StyleSheet's theme. In this case it's Bootstrap. The page could specify the theme or the site could have the theme as it's default. The latter is most often the case and easiest to support.
It is possible to put the CSS styles directly into the dynamic block. I do not recommend doing this as it's difficult for reuse and supportablity.
