Kitchenaid side by side has leak in the water line.

Have you read the owners manual?

to the back of the refrigerator, now there is what appears to be a leak in the line inside. Can someone tell me how to get to it?

Those are well noted for not providing any useful information.

Have to take apart the inside back of the refrigerator compartment. I wonder if the actual problem is a clogged drain for the defrost cycle. The OP didn't provide much information.

probably a leak at the solenoid valve, the fittings leak and i had a valve fail too.

Check to make sure the defrost drain is not blocked or frozen. I had a similar problem with a GE. The defrost cycle comes on at 18 hour intervals. The water could not drain into the drain pan so when the ice melted it would leak out onto the floor from the door of the freezer.

About the same as replacing an external supply line causing a leak inside the refrigerator. It's just a suggestion to look for. His leak may not even be related to the supply line replacement.