If you go into 'Settings' and expand 'Style Sheets' you can see the current stylesheets.
Stylesheets in NovusCMS conform to the CSS industry standard. To create a new style sheet, right click the 'Style Sheets' and select Create.
Then, to use this style sheet in your NovusCMS Site, you will need to add it to whatever template you want it to be used with. You will notice that when editing a stylesheet, it will give you the link to the stylesheet at the top, such as: '/css/Menu.css' (it will always begin with '/css/'
Open the template that you want to add these styles to and in the head section (the section between < head > and < /head > , you will need to add:
with the '/css/menu.css' being the link to your Stylesheet.
If you are interested in adding styles to the styles dropdown menu in the rich text editor, you can go to this Knowledge Base Article to find out more about that:
If you need to learn a bit more about HTML and/or CSS, these sites have some good tutorials that can get you started: