How to connect html form, css, and javascript [closed]

I put in all the code in the html form, css form, and JavaScript form, but I can’t figure out how to connect them all. I have the code so that it will all together create a dropdown box, but it is not working. I put the links to the css and JS in the html form, but when I go to the web page created by the html form it does not show a dropdown box, it just shows the things that I put in the html form, which is just the title and the options.

I tried to put the link thing where it goes like and it didn’t work. I did the same for the stuff you put to connect the JavaScript, but that didn’t work either. In the end, the web page just showed the title and the options that were going to be in the dropdown box.