Absolutely! You can enter in the information you do have, while skipping over the sections that you are still waiting on information for. When you have done as much as you can do, you will be able to save your progress, log out and come back another time:

1. At the top right corner of the computer screen you will 'My Account' click that. Another screen will open

2. Click 'Save and Sign out"

You are all set!