Answer from a Psychiatrist.
The easiest way is to see a family physician with expertise in mental health or see a psychiatrist. Other mental health professionals such as mental health nurses, clinical psychologists etc can help. They would have to get a proper assessment. Some people are not depressed, but are just overwhelmed by work or daily hassles. For the diagnosis to be made, there have to be symptoms of depression, distress and impairment in carrying out one’s roles. The mental health professional can then discuss treatment with them.