Load up Warband Native.
Start a single player game.
Go to the Training Field.
Enter options, set blocking to "Manual, by mouse direction" and Battle AI to "Low".
Ask the Veteran Fighter for a duel.
Try to block all his attacks.
When you can block all attacks for 30-60 seconds, set Battle AI to "Medium" and repeat.
When you can block all attacks for 30-60 seconds, set Battle AI to "High" and repeat until bored.
This will give you intensive basic manual block training, which is the most basic and necessary skill to survive in cRPG. You'll do significantly better after this.