Cambiar planes de entreno
From the document Using Garmin Connect Training Plans | Garmin Customer Support:
Training Plans are accessed from Garmin Connect web. A limited number of training plans, including the Garmin Coach training plans, can also be accessed from the Garmin Connect app
So, if the concerned training plan is not visible on your app, set it up on GC Web, as Andy suggested. It may then appear on the app too.