Writing to a congress person is easy! There are sample letters and bills to choose from on the WRITE page.

www.visitthecapitol.gov says this for why to write to congress: 

People write to Congress to share their opinions on issues that are important to them. Members of Congress consider those opinions as they make decisions about bills and laws. Sarah Hale, an American writer, wrote to members of Congress and Presidents for 30 years asking them to make Thanksgiving a national holiday.