Answer
Hi JC,
Here is a custom CSS code which will turn the menu into a horizontal mode. Please paste it into the "Additional CSS" field, in the widget menu of your main blog widget. It is the dark bar with the text "blog starts here".
.menuBlogCatBtn{float:left; margin-right:10px;} #blogCatMenuContainer:after{clear:both;}
The width of the menu is determined by the width of the category widget (It is the shorter dark bar with the text "menu", above the sample button). Please resize it horizontally to leave enough space for your upcoming menu buttons.
Also the option "Separate buttons by:" in the category widget's menu must be set to "Adding spacing between buttons". Separator lines would interfere with the above code.