You will be opening a file from Dropbox, editing the file and saving your file into your classes DropBox folder.
Open Finder --> find Dropbox in the top left corner and click on it
Find your classes folder double click on it --> Find the file MSWordWhatCanItDo double click on it
This will open a file from a template. Follow all the instructions in the document.
To save the file you will go to File at the top, if you clicked the green button to maximize the file you will have to bring your mouse all the way to the top of the screen to have the menu bar come down. Click on File --> Save As.. --> you will have a window open. If it is small click on the downward facing arrow to expand the window.
In the box next to Save As: put Word Your Name. This will give your file a name.
Now you need to tell it to where to save the file. Find Dropbox on the top left side of the window. Click on Dropbox, find your classes folder and double click on it. Now you can click the Save button in the bottom right of the window.