The diary activity feed shows you feeds of activity for yourself, mentions of you, your Friends, and Circles you belong to. To get to the activity feeds, first click on the site main menu, and then click on Profile:
On the Profile screen, click on the dropdown for Settings:
On the Settings dropdown, click on “Password and Email”. This will take you to a screen that shows your current email address and may be prepopulated with your current password.
On this screen, you can enter your new password – be sure to use a strong password, and enter the same password in the Confirm box. Once you click the Save Changes button, your password will be updated.