You can reset your password by going to the login page at app.motivosity.com. If you type in your email address into the username/login box, you can then press 'I need my password' to get a reset link sent to your inbox. This reset link will be sent from firstname.lastname@example.org and you will be able to use that to change your password and login to Motivosity again. (see image below)
This reset is for forgotten password only. If your issue is with an incorrect email address, or another similar roadblock to being able to log in, you will need to contact your MV administrator over there to help you change any information linked with your account. You may know who this is off the top of your head. Your manager and peers likely know who it is, but as a last resort, you can also find out by clicking the 'Create new ticket' button in the top right, or by emailing in to email@example.com asking to be connected with your admin.
NOTE: Your company may be using a Single Sign On integration that allows you to log in using a company email/password at a central location, then it forwards you into Motivosity. If that is the case, you will not see a 'Sign In' box like the one pictured below. All issues with SSO will need to be solved by your internal IT team.