You can switch  two ways:

1 - Touch on 'Change' on the HOME Dashboard. A popup will show you all of the other workout programs to choose from. When you select a program, it will ask if you want to change just for today, or to switch programs. 

OR

2 - Go to  ME > PROGRAM > Scroll down to Training > select your new plan! It will ask if you want to switch just for the day or fully switch to that program. Select what you would like. 

If you are wanting to completely start a new transformation over you can do so on the same page! Instead of scrolling down to Training, you will simply scroll all the way down, then select BEGIN NEW TRANSFORMATION. If you begin a new transformation, it will ask for your height and beginning weight stats again, but it will also allow you to choose a different program and change your goals.

If you restart your program, your past program will disappear and become a clean slate for you to start over. Both are great options, but if you want to keep in your history the record of what you've already done, be sure to choose BEGIN NEW TRANSFORMATION instead.