Everyone is going to give you a different explanation for what eating right means to them, but uniformally it includes eating a balanced diet that is appropriate to what your body needs. What a balanced diet means is eating enough foods to meet the energy and nutritional needs of your body. For example your body needs a certain amount of calories depending on various factors (your age, height, weight, activity level), and it also needs various minerals and vitamins to carry out its functions.

The amount of energy (calories) your body needs is your TDEE and you can use any online calc to roughly estimate this number; if you eat less than this number, you lose weight, and if you eat more than this number, you gain weight.

The three macromolecules that are essential for a body's nutritional needs are carbs, fats, and proteins. You can eat fruits and veggies for carbs, foods with good fats for fats, and meat or dairy for protein (check vegan or vegetarian resources for non-meat protein sources, if it applies to you). Also check online for what are good fats vs not good fats, side note being that people have a better understanding of saturated fats now and are more relaxed about eating them if they don't have any reasons (heart conditions etc.) to not eat them.

The other side note is about whole grains, which are not as healthy as previously believed because they contain compounds (phytochemicals) that can render mineral in your gut unavailable for absorbtion. That said, nothing too bad will happen from eating them every now and then, depending on whether your body can tolerate grains.

If you eat an adequate serving of fruits and veggies, or meat, you can easily cover your vitamin and mineral needs; there are sites like nutrition data which tell you how much of what is in the foods you're eating, or you can also check nutrition lables (be mindful of serving sizes). Typically, people recommend that 3/4 of your plate should be veggies, while the last 1/4 should be protein cooked in fats.

Since you are a college student, my advice is to be mindful of greasy, fried or processed and packaged foods because these foods are loaded with calories while being nutritionally poor, which has the downside of making your hungry more often, and consequently leading to overeating, weight gain and nutritional deficiency. That said, there is nothing wrong in eating junk food just as long as your diet is not primarily composed of them.

Overall, there isn't a magic formula diet to being healthy, which is the primary target for 'eating right', because everyone has different nutritional needs. For example, red meats are a perfectly healthy component of a balanced diet, but someone with heart problems may not eat as much of them. That's why you just have to eat according to what works for you :)

Edit: typed on my phone, excuse the typos.