Although you can start writing a new template totally from scratch, it is of course much easier to take an existing template and modify that one for your needs. Here are the steps that you have to take for accomplishing this:
Copy the default template
Take the default template directory from
{phorum dir}/templates/default and
copy it over to another directory, for example
{phorum dir}/templates/mytpl.
Edit info.php for your template
Edit
{phorum dir}/templates/mytpl/info.php.
In this file you have to edit at least the $name
variable, e.g. to $name = "My very own template";
You can hide the template from the user template selection
boxes by setting $template_hide = 1.
If you do this, you can only select this template through
the admin interface.
Configure Phorum to use your template
Open Phorum's admin page
{phorum url}/admin.php and go to
"Default Settings". There you will find the "Template" option.
Set that option to your own template. All forums that
inherit their settings from the default settings will use the
template automatically. For other folders and forums, you will
have to go to their settings pages to set their template to
the default template as well.
That is it! You are now using your own template. From here on,
you can start tweaking the template files in your
{phorum dir}/templates/mytpl directory.
Phorum uses its own template language to allow for dynamic templates without using PHP. More information on this can be found in the section about the Phorum template language.