How do I get rid of these little brown dots I have on my arms and cheeks?

First find cause. To figure out the best treatment of the little brown dots on your arms and cheeks, it will be important to find out what the cause is. Freckles? Sun damage? Post inflammatory hyperpigmentation? Your skin type is important as well. You may want to start with having your primary doctor have a look at the areas and recommend treatment. A dermatologist or cosmetic surgeon can be helpful.
Derm eval. These lesions need to be visualized & a history needs to be obtained in order to make an accurate diagnosis. Sometimes lab testing or biopsy is necessary.