Configuring Custom Shipping Costs Based On Order Total.
How do I offer free shipping on all orders above $25?
If you are using real time shipping rates, you'll need to change it to Tiered price based shipping. Navigate to Settings / Shipping / Edit / Tiered price. Then choose how many tiers you will need (in this case 2). Then click Next to page 4 where you can select the minimum order amount ($25) and the corresponding shipping price ($0).