P0305 Code and How to Address

Hey guys, just threw a P0305 code on my stock 2005 ford crown Victoria LX Sport 146,722 miles, just curious on where I should begin to troubleshoot, the misfire isn’t super serious it feels, there is a very mild vibration at idle and at start but it’s driving in gear smoothly, just curious on where I should start for the repair, I’ve only driven about a mile on the car since, and I want to repair it as soon as possible