Hi Barky, There are loads of HTML threads to be found if you search the forum, also have a look at the FAQ thread.

Line break is easy - just add <br> at the end of the line. 
Paragraph break is <p> but you are better off using the line break.

The font settings you mention need starting and stopping.
Bold is <b> to start the bold text and </b> to end it.
Italics are <i> and </i>

There is nothing to stop you doing <b><i> to get bold italics but remember you must close them when finished otherwise all the posts in a thread could end up in italics or whatever.

Jon