I managed to solve my problem by using an if statement and adding break.
{
// Adding first genre title
string[] lines = File.ReadAllLines(@"C:\Users\James Dunn\Documents\Visual Studio 2012\Projects\Assignment 2\Assignment 2\MyJukeBox\bin\Debug\Media\Genre.txt");
for (int l = 3; l < lines.Length; l++)
{
mediaLibrary[0].Items.Add(lines[l]);
if (l == 4)
break;
}
genreTitleTextBox.(mediaLibrary[0]);
}