Yes, you'll have to reset your password when you claim your HarvardKey. But once you set your new HarvardKey password, you will no longer be subject to the annual change requrement. (Please remember, however, that it's important to change your password if you ever feel that your account may have been compromised or your password exposed to others — even unintentionally.)
After you change your password, you'll want to make sure that you update that password anywhere that it might be stored, such as in your email preferences or apps on your phone or tablet — particularly since repeated login attempts with the wrong password may result in your being locked out of your account. For more information on synchronizing your passwords, see Step 3 in this guide (instructions are for HarvardKey password changes, but apply to other login types, too). If you're confused about which login type gets you into which application, check this itemized list of applications' login types, organized by School. Please note that after you change your password, you may need to log in again to any other HarvardKey-protected applications or browser windows you have open at the time of your password change.