The buttons to get you from screen to screen in the scheduler are labeled "Next" and "Back" by default. If you want to change them to read "Next Step" and "Last Step", for instance, follow the steps below.
First, go to Setup->Scheduler
Then expand the Welcome panel and find the Next and Back button label fields:
Change these to whatever text you want represented then remember to hit "Save" at the bottom of the scheduler screen to commit the changes.