There are two ways to do this: via the product page or by using the advanced search page.
1 – From the product page.
In the Product Information section at the top right, go to ‘Attribute Set’, click on the drop-down list and select the attribute set to link to the product.
A window will appear asking you to confirm your choice; click ‘Yes’ if you wish to confirm.
2 - From the advanced search page.
Select the product type of your choice, filter the product(s) to match your set of attributes, and click ‘Select all results’
Click on ‘Actions’, then on ‘Attribute set selection’.
In the window that appears, scroll down the list and select the relevant attribute set, then click ‘Apply’.
If you need to link several products to several attributes sets in bulk on the PIM, you can read this article, which will explain how to do it.
Keywords: PIM, products, attribute set, product record, advanced search, product record completion.