Just few simple steps allow you to integrate your custom template (html/css) into your wordpress site. Do not go through long documentation just follow below steps to integrate your template.
Steps:
1) Go to wp-content\themes\Directory
2) Choose any simple theme folder which you think easy to modify(especially choose default theme).
3) Put your CSS, JS and image stuffs there in that theme folder.
4) Next, Open header.php file include your js, images and CSS exactly the same way as wordpress includes.
5) Put your header HTML from your already sliced HTML/CSS.
6) Same way do that in footer.php, put remaining HTML.
You need to careful when putting your HTML into header.php and footer.php that opening and closing tags should be proper.