how can you use the concept of genetic inheritance to disprove Lamarck's idea of the inheritance of acquired?

When daddy gets a scar, or circumcized, the son isn't born circumcized or with a scar.  The information doesn't get recorded in his genes.

Lamarcks theory was that if an animal were to use a part of its body a lot it would grow to be bigger and better
example: Once upon a time, a dude wanted muscles. So it then worked out so that he got big muscles. Then all his children had big muscles without working out.
Genetic inheritance is that a creature passes its GENETIC traits (such as hair color that u are born with) generation to generation. Muclses aren't genetic, so  they aren't passed on. A body builder's children still need to work out to get muscles. Thus Larmarck's theory is wrong.