Bill,Define what you want to do a little more carefully, colors of LEDs, quantity, that sort of thing. You must have a resistor, or an equivalent.
Red is a good color, each LED will drop around 2.5 volts. They can vary depending on the specs, so that would be useful, but for now I'll assume 2.5V Vf (forward dropping voltage).
If you have 12V (2 6V batteries in series) then you can have 4 of these leds per chain, each with it's own resistor. If the LEDs take 20ma (0.02A) then it goes something like this...
4 LEDs at 2.5V drop 10V
12V - 10V = 2V
To calculate a resistor for 20ma then
R = 2V/0.02A, or 100Ω. A ¼W resistor will work fine.
This is an illustration from the article I recommended you read. If you want to make sense of it, then follow up and read the article.
I snagged this from a post you did earlier.
This is the basic idea of how to light all of the LEDs? It's that easy?
Anyone can reply. I'm not singling Bill out
Jim