Steve B wrote:
Yes, 12v dc. Low amps, low watts, ...

Well, you will need to be more specific. Without knowing the number of
lights and the current each draws, you can't know what rheostat to get.
E.g., a randomly picked one could be such that a very small turn could
turn the lights off entirely, or a complete turn could have very little
effect. And the wrong power sizing could result in it going up in smoke.

Did any information come with them? You certainly know how many of them
there are. How many LEDs in each fixture? We gotta have something
here. What you're asking is like "My car won't run, what size bolt do I
need?".

Bob