Okay, pretend you are finding the least common multiple between 2 and 12.
First, you find the greatest common factor. You do this by getting factors that are prime numbers.
The factors of 2 are 1 and 2, right?
The factors of 12 are 2^2 (That just means 2 to the 2nd power which equals 4) and 3.
So the greatest common factor is 2, because they share a common factor of 2.
Then you do LCM(2,12). 2x12 is 24, right? Then you do 24 divided by the GCF which is 2 in this case.
24 divided by 2 is 12. 12 is your least common multiple.
This is the "quick way" to do it. There's also another easier, but longer way to do this. I can explain it to you if you don't understand this method.
Hope this helps!