You wanna change your password because you are worried that someone else has been accessing your account. Even if that isn't the case, it is a good idea to change your Facebook password from time to time to stay protected your account. If you want to know how to change your Facebook password in just a few steps:
Mobile:
Step 1, tap here and go to Password Tab
Step 2, enter your Current password, New password and Re-type new password
Desktop:
First, you have to log in Facebook. If not yet, please click here.
Then, change your language to English if you use other language.
Next, click here and you can change your password from your Facebook Settings. Type your Current, New, and Retype New password:
Click Save Changes and done: