Look at these examples.
Note that to express a/an + [singular noun] in Spanish, you use either un or una, depending on the gender of the noun it refers to, as follows:- una for feminine singular nouns
- un for masculine singular nouns
Tengo uno coche.
Tengo un coche.Uno is not an article, but the actual number one, and it works as a pronoun. See also Using numbers as pronouns.