Lets try drawing a diagram for the following equation

First we will draw a slow moving neutron being absorbed by the U-235 nucleus, then draw the two daughter nuclei Ba-141 and Kr-92, finally draw 3 neutrons leaving. 

You should be able to draw simplified block diagrams like this, provided it is clearly labelled such as the one above. If you want to you can draw the tiny circles to represent the protons and neutrons, but this is probably not needed.