Enroll in an English class at your local community college or start working on a good online program (see Resources). Buy an English dictionary and grammar book. If you need help, ask a librarian for recommendations.
Start a vocabulary book. When you run across an English word you don't know, write it down in your book, look up the meaning and write a sentence with it to reinforce the concept.
Buy an English newspaper. Sit down with a pen and underline all the words on the front page that you already know. Go to the business section and do the same. Record these in a "similar words" section of your vocabulary book.
Listen to English radio. Concentrate and listen to the sound and flow of the English language. Whereas French has a sing-song rhythm, English is more like marching.
Download a translation program and start an English diary. Write about what you did during the day or how you feel about learning English. Get in the habit of writing every day. The topic doesn't matter as much as the process.
Listen to English music. Pick the genre you enjoy and find English artists. Rap is good for this exercise, as the words are frequently repeated. Country and western music sometimes has easy-to-follow lyrics, so it could be a good choice.
Watch English television. News stations are recommended because generally the presenters speak well. Watch how they move their mouths when they talk and try to copy their movements.
Speak English every day. If you don't have anyone to talk to, sit in front of a mirror and tell stories to yourself. This may sound like a strange exercise, but it is very effective.