If you never manually imported an account key into your wallet, you can alternatively backup your accounts and their funds by exporting the brainkey, a string of words from which your keys are derived deterministically.

To create it, you should do the following:

1. Go to settings 

2. Choose "backup"

3. Choose "create brainkey backup"

4. Enter your password. Press "show brainkey" 

5. Save your wallet brainkey.