How do I alter the days I train on?

I would say that you would want to move it if you just want to move a workout to a more convenient day.  Most people use the 'copy' if they want to copy a strength workout to the next week.

If you want to workout 6 days instead of 5, you can split up a 'two-a-day' for instance.

Let us know what plan you are trying to use and give us a few more details on your schedule and race and we can see more of what you want to do.

Here is some instruction on  Bulk Modification - Copy/Move/Delete