What do you mean exactly by label? A screen shot or public site would help me understand what value you're after.
If you simply want the text from the underlying TextBlock of a Silverlight element, like a TreeViewItem, use the following code:
TreeViewItem tv5 = app.Find.ByExpression(
If the label you mention is actually a tool-tip, that will be more in-depth. See here
for more information.
All the best,
the Telerik team