The exterior part of the knob will have a long spindle attached to it. Put this piece through the latch you just installed. The spindle will now show through to the other side of the door. Secure with plate and provided hardware on the interior side of the door.
The interior handle should easily slide over the spindle. Align the parts and secure in place. Our new knob had a hidden set screw which required a long Allen wrench, provided with the door knob, to tighten in place. Test the new doorknob to make sure everything is installed correctly.