Ok, so this depends on the program type.
Custom:
To send training to clients before they've formally joined the program you need to use the 'Manually Add' option when signing up clients to the program. This option allows you to manually add their name and email.
Once you've manually added them, they will appear in the Pending tab of the Program. Here you'll see an option to the right of their name to add training. This will give you access to their training schedule before they've joined the program:
Once you're ready for them to join the program, click the 'send program invite' button:
Fixed Length:
By its nature this program type requires you to build the training in advance of making the program live. As soon as the client downloads the program they'll receive the training. Remember that you can always update the schedule of the program at any point in time, it's not fixed forever.
Group Rolling Calendar:
Once you've completed the first step ('Info & Pricing' page) you'll be able to add programming to the calendar at the second step, before inviting clients to the program.
Session One Day One:
Exactly the same as a group rolling calendar program. You can build the training in advance and then add clients at a later date.
Remember you can also hide programs from your Storefront and make them private from each program's settings page. See here.
Thanks
FITR