To move a file, click on the options button (three vertical dots) on the file and select Move.

Then, select the folder you want to move the file into. Click Move. 

You can also move multiple files at once.

Hold the Command or Control Key (Mac/PC) on your keyboard and click on all the files you would like to select. You'll see the number of files currently selected displayed above your folders. Click Move in the upper right to select the folder to move your files to, just like when moving a single file.