I have 2 baseboard heaters in my room. The old thermostat has four wires. Two of them on the source side have 120 volts each and the other two are on the load side, one going to each heater. How do I connect my two wire RLV430A to this configuration?

Did a manual not come with the tstat,, I can`t seem to find one online

Here is your manual I suggest you read it. All info you need is in there for wiring but pay close attention to the max draw of 14.6 amps since you are hooking 2 heaters to it. You will need a Amprobe to check the draw or know the watt rate of each heater then convert to amps.

http://customer.honeywell.com/techlit/pdf/69-0000s/69-1855.pdf