User has an email address
If the user has an email address, they can visit http://mindflash.com/login and click the "Forgot password?" link. Now, they can enter their email address. If this is a valid email address in Mindflash, they will receive a link at that email address that will allow them to change their password.
You can initiate the password reset flow, but the user will have to have access to that email box to click the link and change the password.
User has a username
If you have set the user up with only a username and they don't have an email address, then an authorized administrator/trainer/manager will need to go to the "Manage Users" section and change their assigned password.
Note that passwords must contain at least 8 characters, one uppercase and lowercase letter, number, and symbol.