You can check if there is space available and upgrade to Ultimate Boost by following the steps below,
1. Click on the "Promote" icon in the left navigation panel,
2. Select the "Ultimate Boost" checkbox,
3. To complete the upgrade, select "Checkout",
*Please note, if you have already purchased a Top Spot or Showcase against an item, the system will not allow you to select an Ultimate Boost. In this case, you will need to wait for the package that is already in use to expire before selecting Ultimate Boost.