how to add a select box in a region of an created page in drupal

I want to create a list box in 开发者_Go百科a region that has been created by me. Any help would be highly appreciated! I dont understand how to go about it. How can I add just a list box in the existing page?

You should create block (html or php filters should be enabled), put there your list box html code, then place this block into region.
But, using drupal way is recommend - drupal api - create simple module, add form function with list box (select field) and call this form from block hook.