1) Click on 'Manage Inventory' under the 'Inventory' heading in the Control Panel menu. 

2) Use 'Find by ID' or 'Keyword Search' textbox to find the Item. (Or you can use 'filter' icon next to keyword search textbox for 'Advanced Search')

3) Click the 'Edit' icon at the end of your item to go to it's settings page.

4) Click on the 'MARKETPLACES' tab.

5) Under the 'Meta Searches & Website' heading, turn on toggle switches of the Meta Search's you'd like to configure for your item.

6) When you are finished, be sure to click the 'Save' button at the top to finalize.