If you've forgotten your password, just go to my.tanda.co/login and click on either Can't login in? or I forgot my password!. This will send an email to the email address you signed up with to reset it.
If you want to just change your password, while logged in to Tanda, choose Change My Password from the menu in the top right corner:
Note: If you did not receive an email or no longer use the email address in Tanda, you will need to ask a manager to reset your password in My Team. If you are the Owner/Manager of your Business in Tanda and cannot reset your password, please contact support at firstname.lastname@example.org.