Method 1:
Select the Edit button on the product you want to be hidden:
Your page should look like this:
Go to the Publish section on the right sidebar:
Go to Catalog Visibility and select the Edit button:
Select Hidden from the checkbox list that appears and select the Ok button:
Then select the Update button:
Method 2:
Select the Quick Edit button on the product you want to be hidden:
Your page should look like this:
Go to the Product Data section and select the drop-down list next to Visibility:
Select Hidden:
Select the Update button in the bottom right corner:
