You have two choices on how to change your MT4/MT5 password.

First, in the account overview (after you log into the dashboard) you can click on the key of the account on which you want to change the MT4/MT5 password. Then, next to your password click on "Regenerate" and you are done.

Or you can change your password (after you log into the dashboard) by clicking on the E8X of the account on which you want to change the MT4/MT5 password. Then you just need to click on “Login credentials” and next to your password you will click on "Regenerate" and you are done.

But if you want to change your MT4/MT5, you need to have 2FA security.