When you open a spreadsheet, the input line will become the spreadsheet.
The top will be a menu bar with Table, Edit and Maths menus as well as eval, val, init, 2-d and 3-d buttons. To the right will be the name of the file the spreadsheet will be saved into. Below the menu bar will be two boxes; a box which displays the active cell (and can be used to choose a cell) and a command line to enter information into the cell. Below that will be a status line, you can click on this to return to the configuration screen.