Hello, welcome to XenForo!
There is a bit of a learning curve with XenForo style system but it's a pleasure to work with.
Custom styles consist of:
- Style properties
- HTML templates
- LESS (CSS) templates
Style properties control various aspects of the overall design. You can change the color palette/basic colors inside style properties. There are other various things that style properties can help with, such as changing the navigation bar background color or font size for example. Style properties do not cover everything (nor should they).
HTML templates are pretty self-explanatory. The PAGE_CONTAINER contains the bulk of the pages code. Depending on the complexity of changes you want to make, you may need to edit this to change the header/footer. Custom JS can be loaded here as well in the head/body section.
LESS (CSS) templates comprise all the CSS used around the forums. XenForo provides you with the template extra.less to place any custom CSS. Ideally all your custom CSS should go here. You can edit other .less templates directly if you want to change quite a bit.
The more templates you edit, the higher likelihood of having templates you'll need to "update" when XenForo pushes out updates. Updating outdated templates is usually done automatically using the merge template function.
If you're adding a bunch of custom HTML, I sometimes like to create custom templates and include them where you want the code located using:
Code:
<xf:include template="custom_navigation" />
Cleans up the templates quite a bit.
As for integrating a style with any sort of the Bootstrap code. Are you wanting the navigation bar to match and want to integrate all the custom CSS for it? If so, just use the style properties / extra.less template to get the matching results.