How to Contact Senate, House and President
(And be heard!)
Every registered American voter is represented at the Federal level by two US Senators and one Representative in the US House of Representatives (the Constitution guarantees each State two Senators elected in staggered six-year terms and at least one Representative in the House [the total number of US House Representatives and the requirement that they be assigned to specific geographic districts within their respective States based on decennial Census results have since been established by Federal statute passed by Congress]).
The President of the United States, of course, is elected by all of the American voters.
Therefore, if you wish to have the maximum impact on Federal policy decisions and/or maximum assistance with the your issue, you should contact both of your US Senators, your US House Representative (see your State's post-redistricting US Congressional District Map), and the President at whitehouse.gov/contact.