At the top of the plan there is a button that says copy this plan. Click that, and then in the first box, click edit. Change out the date for the date you need. Adjust your walking speed slider if you need to. The next box will let you add your fast passes. If you don't want to change any of your fastpass's, you can click the 'advanced option's button just below, and set it to force the plan to use the fast passes. If you don't check this, you might find that it doesn't want to use the fastpasses you have booked and you would be better off trying to rebook them- but it's up to you. Your ADRs can be added down the bottom of the page- either add meal if it's in the same park, or use add break if it's out of the park.
The optimise button needs to be pushed a few times. Check the numbers at the bottom of the plan. When they stop changing, THEN look at what it's doing. You might want to shuffle a few things around. Use the evaluate button to check how this impacts the times.
Most importantly. Don't Panic.
Also, if you go back to the top box and click edit, there is a button to publish the plans. You can then post a link here and others can check it out and give you feedback if you like.
I hope this helps you.