Bathroom Improvement

I have a very small bathroom. It has no windows. There is only a sink (with no cabinet or storage underneath, just open and ugly), a toilet and a bathtub/shower. I can’t really put anything perm. on the walls. The walls are bright white and their is only really one wall about 4 feet wide that could be decorated since the other walls are taken up by the door, bath, toilet and sink. The floor is grey and white, everything else is just white. I have a small medicine cabinet with the little sliding mirror doors. The door is normal, boring, ugly brown wood. Please help:( Color schemes, storage, etc….

I am home-improvement illiterate, but really need detailed instructions on how to hang the 23” wide, 28” tall cabinet on the wall. It’s probably about 15 pounds (rough estimate) unfilled, probably about 25 pounds filled (another rough estimate).

Thanks!