The first thing we need to know is WHAT YEAR IS YOUR CAR? If it's the '70 pictured, then we know

You may have TWO problems--you may have a bad new battery, or you may have a "drain" when the key is off

For CERTAIN it seems like the alternator is not charging.

For starters, if you have a charger, attempt to charge up the battery. If it's a small 3-5 amp, charge overnight.

Alternator:

Turn key to run, engine off, and use a test lamp or multimeter. You should have close to battery voltage at the large stud output, and at the blue field wire. Probe the regulator connector, and you should have battery there at the ign terminal. (blue wire)

The second wire out of the regulator goes from the regulator to the second (green) field terminal. Use a continuity tester or your multimeter to see if that wire shows continuity. Shake it around while checking

Now, once again, with key on, back at the alternator, unhook the green wire. At the alternator, you should have battery voltage at BOTH the field terminals. Ready up a clip lead and GROUND the exposed alternator field terminal--the one where you unhooked the green. You should get a small spark. Leave this connected and quickly---------

Crank up the engine, and if the alternator is good, you should get "full output" because now you have bypassed the regulator. Take care not to over-rev the engine, because the alternator can easily output too much voltage in this condition. It's helpful--and you should buy one if you don't have one--to use a multimeter and monitor battery voltage

Don't leave this clip lead hooked up any longer than you need to check if the alternator will charge

If you get this far, post back

CHECKING FOR A DRAIN. With EVERYTHING in the car off, and verify that any glovebox/ trunk/ etc lamps are out, unhook one battery cable WITH THE ENGINE OFF and hook your test lamp in series between the cable and it's terminal, see if it lights. A double check is to THEN hook your multimeter in the same connection IN AMPERAGE measurement and see if you can measure any drain. Be careful to start in the highest amps scale.

Here's a picture of the '70 and later wiring. Notice that on the regulator, the IGN terminal is in the "middle" of the connector, and the F field is on the right side, facing the regulator. Down at the alternator, you can switch the field wires and that is OK