When in the 'Personalize' stage of the workflow, click the 'Personalize' button next to an opportunity to begin personalizing.
Here you will see all of the information that is currently associated with an opportunity. You will see contact information which you can edit or rearrange at your own discretion (for more on this, click here), followed by any personalization fields that were retrieved by the system, or still need to be filled in.
Once all of your information is correct, you can hit the 'Submit to Compose' button (or 'Submit for Approval' if you have Approval Workflow turned on) to move that opportunity onto the 'Compose' stage of the workflow. The next opportunity that needs to be personalized will pop up on your screen.
You can also use the More Actions drop-down in the button left to Skip and move on to the next opportunity to personalize.