The people vote for representatives. And then....?
The next step is to watch what your representative is actually doing, let them know if you disagree with it, and vote them out if they consistently act against your interests. Most people don't call members of congress very often, and when they do, things do happen.
You can look at the recent news about the House Ethics Committee for an example: “I can tell you the calls we’ve gotten in my district office and here in Washington surprised me, meaning the numbers of calls. People are just sick and tired,” Rep. Walter B. Jones (R-N.C.) said of the simmering outrage over the proposed change. “People are just losing confidence in the lack of ethics and honesty in Washington.” (https://www.washingtonpost.com/powerpost/gop-to-start-on-amb...)
If you attempt to call your representative's office in DC, either nobody will pick up, or someone will pick up just long enough to quickly talk loudly over you and tell you they do not take calls about your district's issues there, and to call your district's home office.
So you try to find a number for your home district office. If you can find it and call it and try to talk to someone, you will usually either be put on hold, or they will try to find someone for you to talk to, who usually won't be there. So they take a message. The message, written on a post-it note, is filed under "feedback", and not looked at again unless they need to compile a list of popular talking points.
If you are seriously involved in local politics, there are opportunities to meet them in person and tell them about your issue. People with enough time to travel to where their rep is just to tell them how they feel are called "people with no life", unless they do it for a living, in which case they are called "lobbyists". But lobbyists talk with green pieces of paper, and reps hear that a lot louder than people in their district complaining to an intern on the phone.
Yes, it's true that enough vocal opposition can turn a rep toward doing what people want. But it takes too much time and energy and special attention and focus to constantly have to hammer one specific point home to a rep just to get them to do what they said they were going to when you elected them. If they are doing the people's will, usually they lose their re-election funding, or are undone by their party's political machine, or a different one.
The best you can ever hope for is that your party, who is not in the majority, will back your rep, who is not the head of any important congressional committee, on an issue that is against the interests of people with a lot more money and influence than you, so that someone can say they tried to pass a bill. All of that hinging literally on the word of a stranger who told you they'd give you everything you want if you would just give them a job and trust them.
The ethics committe thing is a good example. Everyone, on both sides of the aisle, got flooded with calls because the very superficial idea of limiting or removing an ethics committee seems like a bad idea. What it turned out to be was newly elected officials trying to remove roadblocks to getting changes made so they could reform the system, but people are reactionary and stupid, and that change sounded bad, so they stopped it. What's funny is the party leaders who had been there forever predicted that reaction and told the junior members not to vote that way, because they're good at reading popular sentiment and predicting reaction. Now the old stalwarts look good and the newly elected reps look bad. All because citizens got involved in politics.
The next step is to watch what your representative is actually doing, let them know if you disagree with it, and vote them out if they consistently act against your interests. Most people don't call members of congress very often, and when they do, things do happen.
You can look at the recent news about the House Ethics Committee for an example: “I can tell you the calls we’ve gotten in my district office and here in Washington surprised me, meaning the numbers of calls. People are just sick and tired,” Rep. Walter B. Jones (R-N.C.) said of the simmering outrage over the proposed change. “People are just losing confidence in the lack of ethics and honesty in Washington.” (https://www.washingtonpost.com/powerpost/gop-to-start-on-amb...)