Imagine we start from Change Direction state and we tell FSM to make a decision, it looks at transitions pointing from this state, here there is only one: Move wit condition: Just Do It (which here it means: it always succeeds). Since this tansition condition succeeded, FMS changes its active state to Move state and enemy moves forward for few turns in the direction previously set by Change Direction state.
In the mean time we run decision making from time to time (can be each frame, can be each second - usually decision making runs at slower frequency than game frames, or sometimes it is triggered only when decision making engine receives an event that tells that important change in game state happened and FSM should make a decision about its new state).
At some point when FSM runs its decision making, goes through Move state transitions and finds out that condition of a transition pointing to Wait state reports no more move turns, so FSM changes its active state to Wait which will wait few turns doing nothing.
When there is no more waiting turns left, FSM switches back to Change Direction state, which all of it makes "Change Direction, Move, Wait" behavior of our Enemy. Really simple, right?