Stop smoking. Smoking and other tobacco use narrows your blood vessels. So, less blood can reach your penis. Also, smoking lowers your body's levels of nitric oxide. Nitric oxide signals your body to let blood flow to your penis. Less nitric oxide means less blood flow. Less blood flow can cause or worsen erectile dysfunction.
If you've tried to quit on your own but can't, don't give up. Ask for help. There are lots of ways to help you quit, including taking medication.