From your 'My Hub' page (please see below)
If you hit the 'Menu' icon in the top right...
and select 'Contacts' from the options
Followed by the client profile
You will be able to select any plan they have been assigned under 'Assignments' (Workouts, Nutrition, Programs, Files and Forms) from the list below the client profile picture
Where you can then simply hit the 3 horizontal grey dots next to any plan to 'Edit' 💪