How can I change and update my old password?

Log in to your Simple URL Shortener account and in the upper right corner hover with your computer mouse over your user avatar and click “profile:

After that then go to:
Settings → Change Password and type your new password in the password field:

if you are satisfied with your new password click on the “Submit” button and you’re done!

We do recommend that you use a strong password for your account with a minimum of 7 characters with a mix of upper and lower letter characters plus numbers 1322 and symbols 33%¤#.
Do not use the most common passwords:
Most common passwords by Wikipedia
That will certainly get your account hacked and you do not want that, right? ?

We can also recommend that you use a good reliable password manager such as LastPass which is free, very easy to use and will create make very secure long password for you, (up to 100 characters) without the need for you to remember them.