Spanish is quite different to the English language regarding adjectives. Let's analyse different points:
1. Position: In Spanish, we write the noun first and then we write the adjective. For example:
This is my new car (Este es mi coche nuevo)
Alice has got a red pen (Alicia tiene un bolígrafo rojo)
However, in poetic writing it is common to find adjectives working in the same way to English. But, this is only in literature.
2. Our adjectives are written in singular or plural. It depends on the noun. For example:
These are my two new cars (Estos son mis dos coches nuevos)
Alice has got three red pens (Alicia tiene tres bolígrafos rojos).
As you can check, while adjectives are invariable in English, they can adopt plural form in Spanish. Apart from that, the gender of the adjective depends on the gender of the noun. Pay attention:
I have got two new pencils (Tengo dos lápices nuevos) - "lápices" is male and plural in Spanish
I have got two new houses (Tengo dos casas nuevas) - "casas" is female and plural in Spanish