As you don't tell us whether there are any guidelines in your class or whether you can do anything you want, the best thing you could do would be to research a number of installation artists and see what kind of work they are doing. If you see something you like, let that inspire you.
Another early step you should do is chose a theme or subject you care about. What do you want the installation to be about? Assembling random objects in a room is not an installation, it's random objects in a room. So you have to think what you want to do. It's easiest to do something you know and care about. As we don't know what you know and what you care about, that is a step you will have to figure out on your own. Making art also requires a lot of thinking.
