To update to iOS 5.0.1 you need iTunes 10.5 on your computer. When you've got iTunes 10.5 installed then connect your iPad to it and copy any purchases off the iPad to your computer's iTunes via File > Transfer Purchases. You should also backup the device (right-click the iPad 'device' and select 'back up'), and copy off any important documents, files, notes etc (e.g. by email, the file sharing section at the bottom of the Apps tab in iTunes, wifi, whatever the apps that you use support) - the update process should backup and restore the content but it's best to be safe.
If iTunes doesn't prompt you to update to iOS 5.0.1 on your iPad, then with your iPad connected to and selected on the left-hand side of it, then on the Summary tab on the right-hand side click the Check For Updates button.
Updating to iOS 5 : http://support.apple.com/kb/HT4972