If you have not already registered for a Sprout account, go to https://www.sproutservices.org/register
If you have a Sprout account and need to set/reset your password, go to https://www.sproutservices.org/forgot-password. In the form that appears, be sure to enter the email address you used to register for your Sprout account originally.
An email with a link to set/reset your password should appear in your inbox within 10 minutes. If you do not see it, check your SPAM mailbox as those emails sometimes end up there.
One word of warning is that you will need to click on the link in the email within a few hours of it being sent as it will expire.