Original Patented Treadmill Lubricating System Since 1998 and Official Partner for Major Manufacturers Made in USA (6 Month Supply)

Just apply it directly under the belt. Get a Lube and Walk kit to make it easy, and follow the instructions. Just be careful the lube you already added to the port hasn't in fact come out, as you don't want to over-lubricate. https://www.amazon.com/Lube-N-Walk-Deluxe-Treadmill-Maintenance-Kit/dp/B000AXCF9Q