Watch the Strumming the A Chord online guitar lesson by David Hamburger from Blues Guitar For Beginners
If you're wondering whether you absolutely have to use a pick, the answer is no. The pick is just a tool, and as such it does make certain things easier - strumming, for example, and playing the notes with a certain kind of clarity or articulation. But plenty of great guitarists have chosen the bare-hands approach, including Gatemouth Brown, Albert Collins, Ry Cooder and Mark Knopfler. Give the pick a chance, but experiment without it if you like.