In your Shift4Shop Online Store Manager, you will find a series of Shipping Settings that can be found by going to Settings > Shipping and then clicking on the Enter Settings button under the "Carrier Settings" section.
Once there, click on the + Icon next to "Shipping Settings to reveal a series of checkboxes. Within this area, you will see a checkbox titled "Min. order amount for free shipping."
This field will allow you to set a conditional order amount that will need to be met before the store's automatic Free Shipping* method is applicable to the shopper.
*The automatic free shipping function itself comes into play when your shopper orders an individual item that is marked for free shipping (under the product's Information Tab) or otherwise if their entire order meets eligibility for a Free Shipping promotion via the store's Promotion Manager.
As an example, let's say you wanted to offer free shipping on specific items, but you also wanted to ensure that the free shipping method only applied when orders are over $50. In this situation, you would write 50 into the "Min. order amount for free shipping" field and save your changes. This way, the store's automatic free shipping method would not come up for the shopper unless their order was over $50.
The main thing to keep in mind, however, is that this minimum order amount will also apply to any "Free Shipping promotions you might have created in the Promotion Manager. For example, you may have a promotion created that offers free shipping on orders over $25. In most cases, once the promotion rules are met, the Free Shipping promotion is applied to the user. However, if the minimum order amount for free shipping setting is set to $50, your store will not display the automatic Free Shipping method until the shopper reaches that goal.
The default wording of the automatic Free Shipping method is simply the phrase "Free Shipping." However, you can change this to your liking in the Shift4Shop Online Store Manager's "Store Language" section. The Store Language section can be found by going to Settings > Design > Store Language. Just perform a search for the phrase "free shipping" to find the section.
A good suggestion would be to edit the label so that it reads "Free Shipping (on orders of $50 or more)" so your shoppers are aware of the offer.