Hi Larry,
Never fear! Where there is a will, there is a way.
You might be able to re-heat the ends with your iron and coax them apart while they’re hot. If this just makes a mess of things, leave them as-is and you can glue the end of the seam fabric to the outside of the floor. In Step 3 you will add some glue to the inside of this area anyway to ensure it’s airtight.
I will take a look at the instructions and see if I can flag this better so others don’t make the same mistake. To be honest though, I’ve done the same thing myself on once or twice, so I don’t know how much it’ll help!