Those are html & css files and Fork needs template (.tpl) files with pre-defined areas for the navigation, content blocks, etc... So you'll need to make a new theme for Fork CMS and have a good understanding of HTML & CSS.

It's quite a large theme with a lot of different page structures (different template files (tpl) needed). And a lot of pages where a module or widget is needed. For example: the slider on the homepage will need to be a custom-made module. Fork CMS has a slider but only for images with a title. No youtube embedding or parallax effects etc. The bootstrap theme also has a Portfolio page. You can use the Fork Projects module to create something similar... You can use the built-in Fork CMS blog module for the blog section. The Fork CMS twitter module for the twitter widget, ...

I suggest you start by creating a new theme (copy triton theme and start stripping the code to have a blank theme). Create a few template files (.tpl) with most of the HTML syntax from the theme. I suggest you create a new css stylesheet and you paste only the css codes that you need. Gradually transfer the bootstrap theme to a theme that can be used in Fork.

You can also try to use the css file from the bootstrap theme (instead of starting a new stylesheet and copying them gradually) but I think some selectors won't match the html output from Fork cms.

For example the generated menu/navigation in fork will have a different html output than the navigation in your bootstrap theme. You can: try to style the Fork navigation with CSS code until it's the same as the bootstrap theme, or add a navigation.tpl where you add classnames to the html elements so the css from the bootstrap theme will get applied...

This is probably all very confusing. If it's the first time that you'll be making a Fork theme, read a bit in the Theme guide. But I think you'll learn the most by studying the default Triton theme in Fork CMS. Don't hesitate to ask questions if you don't understand something.

EDIT: Take a look at the Bootstrap theme for Fork CMS by Koen. This uses the default bootstrap theme. I think you can start with this theme and add your custom bootstrap theme's css file to it. You can start modifying this theme, start creating tpl files with the right layout, adding modules to Fork and overriding the html & css, ...

If this is your first theme for Fork CMS, I'd suggest you begin with something a bit simpler. There's no easy way to import the entire Unify theme. It's definitly doable, but there's a lot of customization to be done.

If you have any questions about the Boostrap theme, don't hesitate to ask them. I'll try my best to assist you where possible.