The first step is to define the problem—i.e., to ensure that you are focusing on the correct problem, not on just a symptom or a less critical problem. This step is about identifying what you should be doing.
Second, you need to diagnose the problem: understand its root cause(s), which may be facilitated through using a diagnostic issue tree / diagnostic map. This step is understanding why you have the problem in the first place.
Next, identify all the potential solutions before deciding which one(s) to implement. This is how you can solve the problem.
Finally, implement the solution(s): convince your team/boss/client that the solution you selected is the right one, implement it, and monitor its effectiveness. This is the do part.