@judoclubperon require and import are both ways to get objects and methods from another module. In WixCode, if you use require (the second line) it will mark it with red in the editor, but it will work in run time. So if you include that line, you don’t need the import line.
Regarding where to put it, it depends on your flow. Assuming you have some data on the client that you want to pass, and maybe some more data in a collection, you can use jsw file, and have a button on the client that will call your backend function in its onClick handler. For that part, see documentation and examples here: Velo Web Modules: Calling Backend Code from the Frontend | Help Center | Wix.com
Hope that helps. If you describe your flow I can try to give you more pointers where to start.
If you’re not a developer you might want to consider hiring someone.
If you’re a starting developer, it’s a good excersize 