I think you are talking about Editor on question page....If you are using Snow theme than in qa-theme.php find code on line #11 or near
Find:
$this->output(
'<SCRIPT TYPE="text/javascript">',
"if (typeof qa_wysiwyg_editor_config == 'object')",
"\tqa_wysiwyg_editor_config.skin='kama';",
'</SCRIPT>'
);
Replace:
$this->output(
'<SCRIPT TYPE="text/javascript">',
"if (typeof qa_wysiwyg_editor_config == 'object')",
"\tqa_wysiwyg_editor_config.skin='kama';
\tqa_wysiwyg_editor_config.height='800px';", // change 800px with whatever you want
'</SCRIPT>'
);
If you are not using Snow theme than place this code into function head_script() in your qa-theme.php file something like below
function head_script()
{
qa_html_theme_base::head_script();
$this->output(
'<SCRIPT TYPE="text/javascript">',
"if (typeof qa_wysiwyg_editor_config == 'object')",
"\tqa_wysiwyg_editor_config.skin='kama';
\tqa_wysiwyg_editor_config.height='800px';", // change 800px with whatever you want
'</SCRIPT>'
);
}
Edited Answer
If you want to increase font size too than add below code at the end of qa-style.css
.qa-template-ask #title{
font-size: 32px; //change with yoru value
}
If you want to change only field height than use below code
.qa-template-ask #title{
height:60px;//change with yoru value
}