[aznatama]

You mean a clear bra? Be careful of the type you use, since some of the cheaper stuff is not UV stable and will turn yellow.

you will want to get the paint corrected before applying, or at least fix most of the deeper scratches and imperfections. small scratched will likely be unnoticeable. We really need some pics of what issues your front bumper has before we can suggest a course of action though.

Also, if you have no idea how to apply it yourself, get it professionally installed. It doesn't appear hard, but it's still an acquired skill that not everyone can do properly.