Change default search result to display orderby multiple meta keys

I am using PremiumPress responsive directory themes for my WordPress website. The theme has 4 type of listings assign by meta keys, such as: Frontpage Featured Topcategory Regular listings that assign no meta key My site is working good and everything is fine, except the search result ordering is not what I want. Right now, I can set the default search result to display order by date, title, modified date, and post ID. After the search is executed, I can sort the search result by featured listings to show first, but that's not what I want. I want it to be automatic default to the search. So, I want to you add default search result order by the above listing types in the following orders: Frontpage listing - show first Featured listing - show second Topcategory listing - show third The rest listings - show last. I think the PremiumPress theme is ready to work as above, but the theme developer just didn't put a code into the function file. Let me know should you need more information. Thanks