First, you want to make sure that you tell EnergyPlus to calculate how beam falls on all interior surfaces of zones. You do this by setting the Solar Distribution input field of the Building object to 'FullInteriorAndExterior' or 'FullInteriorAndExteriorWithReflections' (the second option accounts for reflections off surfaces outside of the zone. Otherwise, EnergyPlus will assume that all beam radiation passing into the zone falls on the interior floor only. For more information, look at some other posts regarding solar distribution here and here.

After doing that, the next step is to tell EnergyPlus to report solar radiation values for the interior wall. Do this by adding an Output:Variable object to your input file that ends with IDF. This should report the output variable for 'Surface Inside Face Solar Radiation Heat Gain Rate' and reference the name of your interior wall surface. For more information, look at some other posts regarding surface output variables here and here.