User-defined angular distribution

Hi all,
I want to use txt file were I defined the angular & Energy distribution as input of my simulation
Can anyone explain clearly how to make use of the this file as input source for my simulation (using exgps)

Header of my txt file

theta [mrad] Phi [mrad] gamma [mc2 units] *
-1.000000000e+03 -1.000000000e+03 1.988639823463929757e+00 *
-1.00000000e+03 -1.000000000e+03 1.988639823463929757e+00 *
-1.00000000e+03 -1.000000000e+03 3.557048541157127097e+00 *
-1.00000000e+03 -1.000000000e+03 5.125457258850325104e+00 *

Thanks for reading and for any help!