Student's diets stereotypically consist of junk food, alcohol and anything that can be micro-waved in the Hollyoaks ad break. However no one can live like this forever, so try to eat healthily. The Union has information on healthy eating and recipes you can try, you never know you could become the head chef of your kitchen.
Once you've made a few friends you might find it works well to share food between you and sharing cooking. It can also work out cheaper to share foods which on your own you might not manage to eat otherwise.
The medical centre can also give you advice if you are thinking of changing your diet, they also have a visiting dietician if you want help in losing or gaining weight at a sensible rate.