To dial a number in another country, you first dial the international access code for your country, then the code for the country you're calling, then the actual phone number, usually omitting the first zero if any.
The international access code for the US is 011.
The country code for Australia is 61.
So that would make it 011 61 131542 for your example.
However, that will likely not work. The Australian equivalents of the US 1-800 numbers are 13 numbers (as well as 1300 and 1800). They are calls that are charged at a local rate. The downside is that they're often not available from abroad, likely because the owner is charged the actual cost of calling the number.
However, Kia has a dealer locator that shows phone numbers for those dealers. Those seem to be regular phone numbers that are callable from outside Australia. Pick one of those and call them, either doing your business with them directly, or asking them for a number to call from abroad.
Alternatively, you can call Kia USA and ask them for a number to call Kia AU on.