Creating Lists in Contacts

I am unable to add cards to lists. I follow the instruction to drag a contact to a List that I have created and named but the contact does not appear in the list. I click on the contact, hold the click down and drag the symbol over the list name but when I release the click the symbol springs back . Is there any other way to add contacts to lists?

In the past I was able to create lists but for the past year or so nothing seems to work