There are 3 ways to set/reset a User's password:
1) You can navigate to the User's profile (Setup > Users), and select "Actions" > "Reset Password", as shown below:
2) The User in question can navigate to app.samanage.com (or whatever your organization login URL is), then select the "Forgot your password" link, which will then take the User to the password reset page:
3) The User can navigate directly to the password reset page (https://app.samanage.com/password/new):
NOTE: If a User has been locked out of their account due to too many unsuccessful login attempts, they will be locked out of their account for 30 minutes as a security precaution. After the 30 minute lockout period, the User will then be able to reset their password and log into Samanage.