should i need to install wordpress again for another WP site on same hosting if not then how i use Same WP for new site.
If you want to share the same core with a different website you need to enable the Multisite feature: http://codex.wordpress.org/Create_A_Network If you want to create a separate installation then you need to create another MySQL database, import data from the previous one and do the same thing with files.
If you want to change the directory then just go to Setting> general and change the link where you want to wordpress view and then move all files to that directory from cPanel. If you want to add different content on other wp. then you need to install it again.