How to add points using User Points in Drupal 6 I want users to be able to give points to other users through "User Points" 

I think it's the API: http://drupalcontrib.org/api/drupal/contributions!userpoints!userpoints.module/6
http://drupalcontrib.org/api/drupal/contributions!userpoints!userpoints.views.inc/6

I don't want to use views module, I'm looking for a PHP code to place it in template and to give point.

Thanks
Check nodevote module. It does something similar. You may use it directly or base your code on it.

If you want to use a more sofisticated solution with VotingAPI you can use  userpoints_votingapi and use rate module for the widgets

Cheers.