asensei always recommends you a workout every time you open the app. Sometimes you may decide that the recommended workout isn't one you want to do, in which case you can have asensei skip that workout and not recommend it next time you return to the app.
To skip a workout and not have asensei recommend it again during that program, choose the Maybe Later option on the up Next conversation, then choose No, Skip Workout, to get a new recommendation you can then choose What's Next.
If you would prefer to choose your own workout, you can do that at any time. Press Hey asensei [+], then choose Workouts, and you will see a list of all available programs. Tap a program and you'll see all workouts in that program. To run a workout tap it once to download, then when the blue download bar has completed tap the workout again to run.