Attach a product to a category?

I am on add/edit product page, I insert all required information, eg description image etc. But when I try to assign the product to a category or sub category (schoolwear -> jerseys) I get the following message " Please make a selection from the list". I think I might have missed out an important step. Please advise.

Kind Regards
Sam

Hi,

In the category selection, there is some checkboxes.
You have to check the wanted checkboxes and click to "OK".
If you change the category or click on the "green arrow" (which allow to enter in the category and so, change the screen), all selected checkboxes would be unchecked.
The popup "Please make a selection from the list" appears when there is no selection.

If you want to select several categories, the best is to select "All sub elements" in the filters (at the top right of the screen).

Regards,