Use a chalk box to snap vertical layout lines on the existing wall outlining where you'll attach the new foundation wall. Check that the layout lines are plumb using a level.
Read the plans for the new foundation wall to determine where you'll place horizontal rebar inside the new foundation wall. Use these measurements to place a pair of marks matching each horizontal course of rebar within the snapped layout lines; this will allow you to splice the new wall rebar with the dowels that will be protruding from the existing wall.
Attach a masonry bit that is a 1/4 inch larger than the rebar that you're using into the hammer drill. Drill holes using the marks you made for reference. Drill each hole one-half to three-quarters the thickness of the existing wall.
Slide the rotating bit in and out of the hole to clean out any debris. Clean the concrete dust out of the hole using compressed air or a wire pipe brush.
Fill each hole with concrete epoxy by placing the tip of the epoxy tube as deep inside each hole as possible. Place the rebar's butt end inside each epoxied hole and push it all the way inside. Allow the epoxy to set according to the manufacturer's recommendations before continuing to the new foundation wall.