Guide to update LastPass Master Password.
Step 1:
Open your google web browser and click on the red box as in the below image. When a new interface opens up, click on vault.
Step 2: You are inside LastPass interface. Click on the top right profile icon that reflects your email and click on “Accounts Settings”.
Step 3: A new interface will open, please click on “Change Master Password”.
Step 4: Enter all details as in the image below. Please make sure the Strength bar is green and press “Save Master Password”.