Assuming LiftSimFrame extends java.awt.Window you need to use the setVisible(boolean) mehod. When you get a deprecation warning you need to check the JavaDocs, they wioll tell you the method that is replacing the deprecated one.
Which is a bad idea for deprecated code. It's deprecated for a reason, and should not be used at all unless you really, really have to. And you don't have to unless you are implementing an interface with deprecated methods (like java.sql.ResultSet).