To sign a transaction using the blitz wallet, please follow the listed steps.
1. Navigate to File, then click on Sign Message
2. Enter the blitz address that you would like to sign
3. Click on Sign Message to generate a signature
4. Copy that signature
5. (Optional) Open up notepad and paste the signature there along with the address you are verifying, as well as the recipients address
6. Click on the Messages tab of the blitz wallet then Start Conversation
7. Enter your address up top, then the recipients address below
8. In the Message box, paste the signature you created earlier
9. Send the message