concentrate on (someone or something)
To focus on a particular person or thing. I'm sorry, but I can't concentrate on what you're saying with that music blaring in the background. If you want to get into the college of your choice, you really need to concentrate on your schoolwork.
concentrate (up)on someone or something
to focus one's thinking on someone or something; to think intensely about someone or something. (Upon is formal and less commonly used than on.) Please concentrate upon Jeff. He is the one we should discuss. Try to concentrate on your work more.
concentrate something on someone or something
to focus something on someone or something; to center on someone or something. Let's try to concentrate our efforts on finishing this job today. She concentrated her attention on Lynn.