is it new? anyways, here's what I do.
take a straight edge
Lay it on the fret board. Ideally it should be flat and touch every fret, or touch at the ends with a very minuscule gap in the middle. This indicate proper truss rod setup with either minor relief or straight. If the fret work is perfect, straight is ok, if not, some relief should be added by loosening the truss rod. if there is some relief and its still buzzing then it badly needs fretwork done. If it touches in the middle of the straight edge and can act like a sea saw, then you have back bow and need to tighten the truss rod.
If the neck relief is not the culprit and you determine the frets are the problem, determine wich fret is the culprit. press on the strings that buzz, where they buzz and work your way up the neck. when the buzz stops you have reached the fret that is to high. Check to ensur that it is seated completely in the groove for it. if the neck is dirty, take a wire brush to the side of the fret and clean away any grime. you are checking for any gap between the fret and the fretboard. if it is not fully seated it should be possible to press it into place, using a clamp and some wood with a towel or something over it to make sure that you dont dent the guitar. set it on there and clamp down, increasing pressure as you go. There are specific tools for this. If you have them or acsess to someone who does, go that route, but this will work.
if it's none of that you need to file down the fret and I would def rocomend you either purchase the specific tools needed or tale it to someone to fix.
check all this stuff and if none of that is the culprit report back for how to do the fret job.