Download the appropriate Autoloader above. Your model number can be found under Settings › About › Model Number
Turn off your BlackBerry 10 Dev Alpha device.
Run the downloaded Autoloader file.
When prompt shows “Connecting to Bootrom”, connect your device to your computer and turn it on.
If you have a password set on your device, type your password when prompted.
After your device restarts, complete the set up wizard.
Note: You may attempt to load the latest Dev Alpha B update onto your Dev Alpha A, however the The Dev Alpha A is no longer officially supported as of 10.1.0.1485. If you encounter any issues please downgrade back to 10.0.10.263 using the Autoloader method. You can download the old 10.0.10.263 Autoloader here.
The 10.2 SDK OS (10.2.1.1927) is also being made available to those developers who would like to test on their BlackBerry 10 device. You'll need to find your device model number and then download the corresponding Autoloader above. The model number can be found under Settings › About › Model Number.