In Spanish, the preposition "de" is used to express that something belongs to someone. It is a very different construction to the English equivalent using an apostrophe: 's.
Have a look at these examples to see how it works:
As you can see, in Spanish the word order is different to the English.
We name the possession first, and then the possessor, e.g "la casa" (possession) "de" (of) "Lucía" (who possesses), literally "The house of Lucía".
Remember that if the article "el" comes after "de" you need to contract the two words to "del":