Here's a quick explanation of two easy ways to enroll a client in a Stridist program.
From inside the program builder, click on the "Enroll clients" button. That will open a list of available clients and groups available for enrollment. Click on the client, and then click on the start date for the program.
You can also enroll a client in a program by visiting the client's program calendar. From there, hover over the day you want the program to start, and click on the enrollment icon. You can then choose from your list of available programs.