The Italian preposition da means "from" in English. This preposition is used in time expressions, in which case you may translate it as "since" or "for." Italian uses the construction of present tense + da + time expressions to indicate an action that began in the past and is still going on in the present. For example:
Da quanto tempo leggi questa rivista? (How long have you been reading this magazine?)
Leggo questa rivista da molto tempo. (I’ve been reading this magazine for a long time.)
Da is also used in the following instances:
1. To express the equivalent of the English phrase "at the house of":
Vado dal fratello. (I’m going to my brother’s house.)
Vado da Filippo. (I’m going to Filippo’s house.)
Andiamo dai signori Rossi. (We’re going to the Rossi’s house.)
Andiamo da Gino. (We’re going to Gino’s house.)
2. To indicate origin or source:
Vengo da Torino. (I come from Torino.)
Vengo dalla Francia. (I come from France.)
è tornato dalle vacanze. (He is back from vacation.)
è tornato dagli zii. (He is back from his aunt and uncle’s house.)
3. To indicate the worth or price of something:
Voglio un francobollo da cento lire. (I want a 100 lire stamp.)
è una casa da poco prezzo. (It’s a house of little worth.)