When you first open your client's plan view, you will see that they already have a plan added. This plan is their current plan. It is basically a weekly schedule of their workout.
The current plan is the plan your client will see by default in their client's app.
To schedule a future workout:
Click on Add Upcoming Plan.
Set up workouts by clicking on the individual day. In each day, you can add Exercises, Supersets, Circuits, and more.
When the plan is ready, set the start date for this upcoming workout plan.
Now on the date you set on the upcoming plan, your client's current plan will automatically be switched to this upcoming plan.
You can add as many upcoming plans as you'd like to schedule workouts for your clients weeks and months in advance.
Further Readings