To change your password, you have to log into your account, and proceed to the security page in your dashboard/profile.
Or just click on the following
link
.
Fill in the form, submit it, and follow the prompt. You have to remember your old password, to change it.
If you don't remember your old password, you have to reset it. How to reset your password you can learn
here
, or directly proceed to the
Password reset page
.