How do i add additional CC account to make purchases?

So I already have one credit card verified on the system that I have been making purchases with. But when I go to make a purchase I do not get the option to add an additional credit card account to which make purchases with. How can I go about adding another credit card to my account? When I go to make a purchase it only gives me the option to choose an existing linked account but does not give me the option to add a new Link account.