There are two basic challenges in Adho Mukha Vrksasana (Handstand): gaining strength in your arms while trusting in your ability to hold your body, and learning to swing the hips up over the head.
If fear is holding you back from trying this beneficial pose, try this:
Start in Downward-Facing Dog (Adho Mukha Svanasana) with your heels at a wall, hands and feet a little closer to each other than usual. Walk your feet up the wall, bringing more and more weight onto your arms. If your arms can support you here, you should have the strength to do Handstand. Repeat this exercise to build both strength and confidence.