I've taken apart and put one of those cheap solar yard lights from wally-world into an antique chinese wrought iron lantern (immitation antique). The solar cell is just below a decorative cutout in the lid and is about 50% shielded by the metal. It doesnt receive enough sunlight in the day to charge the battery to run the light any length of time.

If i wanted to put a second solar cell in under another cutout, would i wire it in series or parallel with the first to charge the battery?

 

In series if you need more voltage, in parallel for more current just like batteries.

If in series the new one should be matched current rating wise to the existing to prevent possible reduction of current available.

If in parallel voltage should be fairly close to the other one.

Large PV panels are made by combining series and parallel wiring to get desired rating.

 

If you're using the same battery and circuitry, put similar cells in parallel. That'll give more current for charging but otherwise everything stays the same. It's nearly the same as just shining more light on it.