There are definitely a number of different ways to attack the editing process.
We recommend looking at dialogue first, as that’s one of the most critical sections of your writing. Is your dialogue really speaking to your audience? Are you using dialogue tags properly? What about adverbs in dialogue?
Then you can take a look at the repetition tab. Here you should be able to clean up words and phrases that you use too often and too close together, making your writing boring.
As a third step, you can explore the Strong Writing and Word Choice sections, where you can just focus on one thing at a time. For example, the Generic Descriptions report under Word Choice will help you focus on wishy-washy descriptions that could use some punching up.
After attacking these sections, you could then run the Pacing reports to look at sentence variation and slow paced paragraphs. (Of course, this may be one you could start with in the very beginning of the process, too!)