How can I set up a 7-day free trial for one of my subscriptions?
A free trial can be offered using dynamic discounts. Dynamic discounts within Bold Subscriptions allows you to offer a 100% discount on the initial order, effectively providing a free first order while maintaining recurring charges thereafter.
More information on this feature can be found here - https://support.boldcommerce.com/hc/en-us/articles/29371478117780-Subscription-Group-Settings#dynamic-discounts.