To use the Achilles effectively, we need to be able to create a very quick stretch-shortening cycle within the ankle. This requires a brief ankle dorsiflexion movement (to stretch the Achilles and store elastic energy), followed by rapid plantarflexion (energy release).
The ability to couple this movement in the ankle is as much coordination as strength, and often needs training. Once this mechanism is unlocked, it can have very positive effects on jumping and running. But if someone progresses plyometrics without this ankle coordination (or requisite calf strength), then the majority of the effect of the exercise will be lost.
Here are some ways of progressing from beginner (standing ankle DF) to advanced (high drop jump, single leg skipping).