I had the same issue! I did not want to do harmonic slur practice because I didn’t know if I was doing it right.

Stick with the process.

Focus on the feeling of the singing c exercises. As you progress through the course, your slurs will be done with less and less effort. I can’t tell you exactly how to do slurs because that won’t help you. You won’t discover it by knowing exactly what to do; you’ll discover it by reinforcing the feeling of correct playing. When that feeling bleeds into your playing, your slurs will be effortless.

Keep practicing the WIHSC!