To rename a workout via left swipe:

1. Tap Training Plan on the bottom menu
2. Swipe left on the workout you would like to rename 
3. Tap More
4. Tap Rename
5. Type in the name and then tap Save

To rename a workout via tap and hold:

1. Tap Training Plan on the bottom menu
2. Tap and hold on the workout you would like to rename 
3. Tap Rename
4. Type in the name and then tap Save