how do I enable the similar question prompt when asking a question?

edit

For clarity I'm talking about the dynamic window below the title and between the body which shows questions similar to the title.

It's running on askbot.org but I don't see an option to enable it in my settings.

Update:

I have tried adding this to MY_SKIN/templates/ask.html:

<script type='text/javascript'>
    var sortMethod = undefined;//need for live_search
    var minSearchWordLength = {{settings.MIN_SEARCH_WORD_LENGTH}};
</script>
<script type='text/javascript' src='{{"/js/live_search.js"|media}}'></script>

and I updated live_search.js from the default template.