Click "Pricing" in the header menu.

Choose the listing you want to create a pricing rule for.

Click the blue "Add Rule" button underneath the graph of your prices.

Open the drop-down "Templates" menu, scroll down to the "custom" rules. This is where you will see the list of rules you have created for any listing.

Choose the rule you want and it will auto-fill all fields. You can then adjust these or just press "save."