Pilfered Milk
Muscle Confusion is real in a sense. It is not really muscle "confusion", the term "muscle confusion" is just a simple way to explain the conjugate method. The conjugate method is used by the most elite training methods, the most well known being Westside Barbell. Crossfitters often refer to the conjugate method as "muscle confusion" simply because it's easier to explain in those terms. Louie Simmons gives a brief explanation of the Conjugate Method
here.
To answer your question, to achieve "muscle confusion" you must swap around different body-part exercises in your training routine so that you are constantly adapting to new movements.
As much as I love the big strong boys and girls at WSB, usually when people are talking about 'muscle confusion' they're talking about doing pushups one day and bench dips the next, or doing squats on the bosu ball or any other such non-productive thing for the sake of making each workout 'different'
The way that louie touches on 'muscle confusion' is still using planned, effective training periodisation that is counter productive for 90% of people, but perfect for his audience, the people with huge squats, trying to develop monster squats.
Most of my clients will cuss me out because I'll have them squatting 3x a week, when they "know" they're so advanced they can only take 1 leg day a week. fast forward a month and they're squatting 30 kilos more than before. They "Know" they've stalled on flat bench and need to do incline bench to develop the anterior deltoids in the rep range of 10-12, and then bam! I've made then bigger and stronger on sets of 6 on the flat bench.
In general I think the teachings of westside barbell are best kept from people till they're squatting double bodyweight.
There is a place for doing different things to make other lifts rise and increase your fitness, but it's not really the same concept as what most people these days are peddling as muscle confusion.