The base shear will be reported in a rectangular block in the output file. This is the file with the .ANL extension.
If you want to know the individual loads generated for the seismic case, wait until the analysis is complete. Then, switch on the load display icon in the Modeling mode. Select the seismic load case from the load list box. This will bring up a number of horizontal green arrows at the nodes. Go to Symbols and Labels and switch on the checkbox next to Display Load values.