how to use data

Dear Teresa,
The detailed photovoltaic model allows you to choose which components of the solar data you want it to read from the weather file. By default, it will read the DNI and DHI data, but you can change it to read DNI and GHI, GNI and DHI, or POA data. The weather file must contain at least the components you choose, and it can contain all three components.
For example, if you choose DNI and DHI, then the weather file may contain only DNI and DHI solar data, or it may contain DNI, GHI, and DHI. SAM will ignore the solar data that is not specified on the Location and Resource page.
To see the options, on the Solar Resource input page, expand the "Albedo - Sky Diffuse Model - Irradiance Data (Advanced)" panel:

Best regards,

Paul.