FN Key how do I disable this key to stop acting as the principle

Hello, I have a HP Laptop 355G2, "new" however I am used to using the f2 key function or the other f keys, however I have to use the FN key then the f keys to get a function
I don't want to use the FN key in this way for instance if I press the f2 the screen goes dark I want the f2 key to do F2: Renames a highlighted icon, if I use the f7 key instead of spell check I get minus volume, how do I disable this key to stop acting as the principle function key but not to disable it completely as it still has its uses,