You can use something like https://www.amazon.com/Arctic-Silver-Premium-Adhesive-ASTA-7G/dp/B0087X7262, or use the black glue from the same website you got the tool, adding more solder to the existing isn't a good idea, you should clean the chip's surface and then start fresh, ensure that the amount of solder paste is equally even across the whole chip.

Watch this video https://youtu.be/5WH7g61d90w, it's helpful