Being concerned *with* something means having an interest in something, or having to do with something. Examples: My son is more concerned with playing video games than with studying. My mother is concerned with her singing group. She spends all her time there. I read a newspaper article concerned with the situation in Afghanistan. Being concerned *about* something means being worried about something. Examples: My son doesn't seem to be concerned about failing in school. I'm concerned about my mother. She spends all her time singing. Don't be so greedy! You should be more concerned about others.

Practically very similar. Most of the time people are “concerned about” something. Being concerned with sometimes implies more to also be involved with something. You might tell someone, “do not concern yourself with such things” meaning they are suggesting to not get involved. If you never use “concerned with” you will be fine. Don’t concern yourself with it. 😆