Begin by learning the English alphabet and the sounds the letters make. The script of English letters is different from Farsi, so it may take some time to learn how to read and write the letters. Watch online videos, such as those found on You Tube, which are geared toward English language learners to help you learn the English alphabet.
Learn common words and phrases in English. These words will form the basis of your vocabulary. Listen to these words and phrases spoken in recorded conversations. You can then begin to listen for how words are put together and for other words that are often used in conjunction with words you already know to build your vocabulary.
Join an online language exchange, such as My Language Exchange. You will meet with a native English speaker who wants to learn Farsi. You will be able to have conversations with a native English speaker on a regular basis. This will help you to improve your conversation skills and your vocabulary.
Listen to English as much as you can. In particular, listen to news broadcasts or watch clips of television shows online. You can hear a variety of English accents from around the world, and you can pause and rewind anything you did not quite understand the first time you listened to it.