如何在不同的分辨率下停止CSS / HTML导航菜单包装？

I am new to CSS but have played around with various other languages over the years. I have successfully added a navigation bar to my website but when viewed in a smaller window or lower resolution the bar wraps itself. I have spent quite a few hours looking around the internet and tried to modify the code in ways which has helped other people but am yet to find a solution. Ideally what I want is for it to re-size as the resolution or window size changes but if that is too difficult or can't be done, just locking the size so the user has to scroll across would also be OK. I am new to CSS but have played around with var