how to update nodes and formating here ?

At a minimum read the three line immediately above the edit pane when you first posted.

For a little more mileage also read the few lines following the edit pane.

If you want to look like a pro and have other monks take an interest in your nodes read and understand all the links following the edit pane and ensure that the preview of your node looks as you expect it to. For reference that material is:

• Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
• Read Where should I post X? if you're not absolutely sure you're posting in the right place.
• Please read these before you post! —
  • How do I compose an effective node title?
  • How do I post a question effectively?
  • Markup in the Monastery
• Posts may use any of the Perl Monks Approved HTML tags:

  a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

• Outside of code tags, you may need to use entities for some characters:

  	For:		Use:
  	&		&
  	<		&lt;
  	>		&gt;
  	#91;		&#91;
  	#93;		&#93;

• Link using PerlMonks shortcuts! What shortcuts can I use for linking?
• See Writeup Formatting Tips and other pages linked from there for more info.

Update: added reference material