"Must" expresses strong advice or perhaps obligation here whereas "would" could only refer to the past here and only fits in specific contexts. Without added context, "must" seems the best fit in general, although the surrounding sentences could certainly change that and make "would" more appropriate. For example: "We once got a new photocopier. We would follow these steps..." It's also possible to use "would" in a more hypothetical context if the sentence were extended: "We would follow these steps to use the new copier, but we found a more efficient method."
Basically, if you take these two sentences exactly as they are without context "must" would be more suitable, but language doesn't work that way so context is key to which is more appropriate.
If you want to look up more specific differences between the two I did the first bit of legwork already: "must" is a modal verb while "would" is a modal auxiliary verb.