Selected products allow you to select the products you want to display on the front page and under each category (which has subcategories).
To use Selected products, go to admin -> "Catalog & Products" -> "Products on the home page" to add a new or change a selected product.
You add a new selected product by clicking on the “Insert new" button.
In the "Product" menu, select the product and in the "Expires" field, enter a date when you want the product to be removed as the selected product.
You can leave this field blank to allow the product to be a selected product until you manually delete it.
When you are done, click the "insert" button.
To change a selected product, click on the selected product you want to change and then on the "edit" button.
Make the changes you want to make and then click the "Update" button.
Read this if the instructions above are not correct in your store In newer versions,
"Selected products" has changed its name to "Products on first page" in admin.