Make sure that you have the (wrap text) option selected for that cell under format. Then hold down the "ALT" key and then hit Enter. Doing this should cause you to go to the next line in that cell.
Hold down the alt key and then press the enter key. This will allow you to write an extra line of text inside the same cell as is currently being used. This can be done as many times as required. When you are done, simply press the enter key to continue.
In order to have more than one line of text within a single cell of an Excel spreadsheet, do the following:
1. ) Either single click within the cell or within the formula bar at the point you want to start a new line. 2. ) Simultaneously press the "alt" and "enter" keys.
To force a carriage return, you must have the input text area selected (the area to the top, there should be a blinking cursor in there), and only then do you hit shift-enter (holding down shift while you tap enter).
note: on a mac keyboard, you have to hit Control + Option to get to the Alt key. Basically, hit ctrl+option+enter add a comment