Instructions
Go to the "Sims 3" official website. Click "The Store" on the upper toolbar.
Click "Hair" in the sidebar, followed by either "Male" or "Female."
Click the hairstyle you want, followed by "Purchase." You will be prompted to log in if you are not already, and then points are automatically deducted from your account. Your "Sims 3" launcher will also load the hairstyle for installation.
Click the check mark box beside your newly purchased hairstyle. Click "Install."