Case 1: Can't remember your password and wish to reset it
You can do this by first clicking on "Sign in" on the Ahrefs Homepage.
Then click on "Forgot password?":
By submitting your account's email address, you'll receive instructions via email on how to reset your password. Simply follow the instructions and you're good to go! :)
Case 2: You know your password but wish to change it
You can do this within your Ahrefs account by following URL https://ahrefs.com/account/my-account and clicking "Change password":
Key in the old password and the new password, and you're good to go! :)