1) in the HTML Editor code on your page, find the following line:
$CKEditor_config["tabSpaces"] = 4;
and change it to:
$CKEditor_config["tabSpaces"] = 4;
$CKEditor_config["enterMode"] = "CKEDITOR.ENTER_BR";
2) In the HTML Editor wizard, click the pencil icon next to the Editor Preset list to edit the preset, go to the Styles tab.
click the plus button to select a css style sheet, then change the body class to the class that you would like to use for body of the HTML editor window.