Adding a Search-bar

Hey guys gotta problem over here. Im actually coding a custom page with a custom design. Actually there isnt a searchform.php or a search.php – okay the files are there but there is no code in it. I just need a normal basic search for my site and want to know what i have to put inside to get the search to work.

Hoping for some help for my problem.

Thank you guys!

The page I need help with: [log in to see the link]