[Aeglos]

Hi im new to this forums and i have loved the tolkien legendarium since i was a little kid. So dont be rude if i ask dumb questions. But one thing i find strange is. At the kinslaying of elves. How did the noldor have weapons. What use did they have in vallinor? And if the valar saw the elves making weapons why didnt they stop them, because there was no need for it, and could only be used to bad things like violence and murder. So what do you think?