Wondering what is the best way to hook up two 4 inch led lights to come on with my high beams.

 

Relay... wire tap the trigger wire from the relay into your high beam's positive wire. Then wire up the relay to your battery and the lights.

 

I'm guessing you are mounting them to the bumper or inside the grill? Personally I would dig out my test light and test the wiring to the headlights to find the high beam and splice into it. You can also splice into the ground wire (usually the white wire) if you need to run a ground.

Use a heat shrink weather proof butt connector though and crimp them good. Gently tug the connection before applying heat, nothing more irritating than having it come apart after sealing it. That works best for keeping moisture out of the connection. You can find them at any parts store or even home improvement stores. Heat shrink tubes are okay but tend to crack and split after just a couple years.

Do yourself a favor and never use the quick connect saddle connectors for any exterior application. Those will begin corroding within a couple of months.

I would suggest using an inline 20 amp fuse and check the heat displacement of the lights (some LED lighting will produce high heat) before you mount them.