How to show label one by one in c# windows application

Set up your timer to the appropriate interval (using the Interval property - remember it is in 1/1000th of a second) then in the Tick event all you cave to do is something like:

myLabel.Text = myArrayOfTextStrings[index++];
if (index >= myArrayOfTextStrings.Length)
   {
   index = 0;
   }

Do note that index needs to be a class level variable, i.e. declared outside any method.