Hello,
1. You need edit the file wp-content/themes/legenda/framework/shortcodes.php (find the section “! Share This Product” in line 1460), to change links you need edit the code, for example for Twitter <a href="https://twitter.com/share?url='.$permalink.'&text='.$text.'" target="_blank"> and replace https://twitter.com/share?url='.$permalink.'&text='.$text.' with a link to your Twitter account.
2. You need use “Banner” element in Visual Composer editor and upload your image.
3. There is no option to put content in the right side top bar. You can add [share] shortcode in Text widget and drag it into “Place in header top bar” area in Appearance > Widgets. Icons will be shown on the left side.
Regards,
Eva Kemp.