
Basically you add a few lines in the module's xoops_version.php module that look like this:
// Search
$modversion['hasSearch'] = 1;
$modversion['search']['file'] = "include/search.inc.php";
$modversion['search']['func'] = "video_search";
and then you must create the include file that defines what to search.
If you go to the module repository and download Video Tube v1.7 you can make a copy of the search.inc.php file found in the include directory and then use that to make your edits for your own module.