Put yourself in commish mode and select the team you want in the Team Menu. Under Advanced in the Team menu select team setup. On that page click Edit Ballparks (Bottom right). On that page click the Pictures & Coordinates tab. On this page next to daytime pic click the ...button to the right and select the pic you want for daytime. Do the same for night pic.
Repeat steps for each team.
Since you're using the all in one pics, do yourself a favor and get those .prk files. Then you can avoid all this and auto import the correct pics in one shot.
