How do I modify my WordPress homepage

please contact the theme’s vendor for support for that commercial theme.

without free access to all theme files, helping through this forum is virtually impossible, or very limited at best.

‘normally’ you would edit index.php, or create home.php from a copy of index.php, if you don’t want the changes to spread into other pages.
however, details depend on your theme.

http://codex.wordpress.org/Template_Hierarchy#Home_Page_display