By default all templates are location in
folder. I have prepared custom theme where you can override default templates by creating identical template path in customtheme folder.
If template is located in
defaulttheme/tpl/lhchat/getstatus/container.tpl.php - it's user status template used to show user status is he online or not.
If you want to override this template you have to create template in
Like in settings/settings.ini.php themes order is in the following order
0 => 'customtheme',1 => 'defaulttheme',
Customtheme has priority against defaulttheme, so that way you can override any template you want without changing default templates. You can also override same way images/css/js and so on. Don't forget to disable cache while developing. Also after you enable cache again, clear it from back office by clicking clear cache.
For native placement template you have to override "defaulttheme/tpl/lhchat/getstatus/native_placement.tpl.php" the most easiest way to override widget interface you which is rendered on site is just override it using css with !important flag.
Also if you are building extension and want to add custom js and css you can override just "defaulttheme/tpl/pagelayouts/parts/page_head_css_extension_multiinclude.tpl.php" multiinclude keyword at the end indicates that each time template is found (let say in another extension) it's included.
If you want to style widget content itself please refer to this article.