documentclass{article}
usepackage[utf8]{inputenc}
usepackage[english]{babel}
usepackage{tikz}
usepackage{tikz-uml}

begin{document}
begin{tikzpicture}
umlsimpleclass{classname}
end{tikzpicture}
end{document}

documentclass{article}
usepackage[utf8]{inputenc}
usepackage[english]{babel}
usepackage{tikz}
usepackage{tikz-uml}

begin{document}
begin{tikzpicture}
umlsimpleclass{classnamé}
end{tikzpicture}
end{document}