a real dumb question I know! but....

When you say 'work together' I gather you just mean working like a typical website. Each page is a separate page. The only thing that links pages together are links from one page to another. So let's say you have two pages, one is your homepage and it might be called index.php or index.html. You might also have a contact page called something like contact.html or contact.php. You simply upload both those page files to your website.

The linking together of those pages simply occurs in the menu system you are using on the website. So your website might have a navigation menu at the top, bottom or both, with links such as Home, About Us, Contact Us, etc. When people click on those links in the menu they are taken to the respective pages. So you just need to make sure that menu is on every page and has the correct links to each page file. So the 'Home' link would link to the index.html or index.php file. The 'Contact Us' link would link to the contact.php or contact.html file.

If you just have a blank form then you need some type of form script to execute that form. There are plenty of free contact form script online, you'll just need to search Google and decide on one to use that suits your purposes.

When you upload a page on the web, it will be available at a specific url. For example: http://yoursite.com/index.html ( main page ).
Then you will have http://yoursite.com/contact.html http://yoursite.com/about.html http://yoursite.com/salepage.html , etc. On all the pages, on the menus, you have to link to all other webpages. You don't need to know the url upfront, you can use relative links, for example you can use only the filename

For example, when you add a link <a href="contact.html">Contact</a>
Make sure that they are linked between before you upload.

To make the contact form to send the email you have to use php. Make sure your server support php, and you should have a page with a php extension. Search on google for "php contact form" and you will find the code.

Btw, why don't you use wordpress ?

Never used komposer but I use dreamweaver. In dreamweaver I start with a template that can be automatically applied to any page I create. That template has the navigation links or menu in the sidebar or across the top, where ever you decide to put the menu. So no, the pages do not automatically link together. They all have to have a common menu with links to category pages which then link to individual pages.