Click the dot and buy upgrades. Click the number to buy the upgrade. If your score goes down, that means you successfully bought the upgrade. If the score does not go down, you did not buy the item because you either do not have enough to buy or you did not click it correctly. LAG MIGHT SLOW THINGS DOWN.
WARNING: DO NOT BUY A UPGRADE MORE THAN ONCE. IT WILL SCAM YOU ON HOW MUCH IT COST.