In the example below we’ll create a intro offer that:

To begin:

click Memberships > Subscriptions and Packs > Add new subscription

Give it a name > then, set a price (can be set to $0 if needed)

Then scroll to Duration Settings > choose Absolute Interval > put 7 days > toggle on 'Purchasable only once'

Toggle on 'this subscription is an intro offer'

Choose what the intro offer can be used on > then click 'Create'

Then click this arrow to back out to the Index Page

Find your newly created promo in the subscription list > flip the toggle on to make it 'Featured at Checkout' for customers

To see what customers see at checkout, click 'Your page'

The promo will now be listed under your Purchase Options