Pushing the Enthalpy button on the Component Properties - Temperature Dependent Properties Window brings up the Component Properties - Phase Window, where you select the phase for which you want to enter vapor, liquid or solid Enthalpy data.
Then you must define the type of data you want to enter - tabular or coefficient - in the Component Properties - Data Source Selection Window.
Finally, enter tabular data in the Component Properties - Tabular Data Window or coefficients of an equation in the Component Properties - Correlation Selection Window.