You have two options:
Changing personal data in your profile: Go to the "My account" section (click on your username in the top right corner) and then go to "Player details". You will find all your personal information here.
When changing your password, click on the pencil and enter your old password. Then enter your new password twice.
If you don't remember your password, log out of your account and the next time you log in, click on the "Forgotten password?" option. You fill in the email address, you used during registration, or your username here.
You will receive an email (don't forget to check your spam folder as well). Then click on the link that will redirect you to the page where you can create a new password. If this doesn’t help, you either contact our customer support in the chat or on the number: +420 910 920 555 from 10:00 a.m. to 10:00 p.m.