If you are logged out of your PIM App (version 5.3.5 or later) you will see a "Forgot Password?" option for you to tap. If you have a user account registered under that email, an automated password will be emailed.
You can use the password you are sent to log into the App, or if you wish to change it, log into your PIM Dashboard and then tap your Profile (top right conrer) and select > Update User Details and enter your preferred password for both the App and the Dashboard.
If your email is not recognised then it may be that you are using a single sign on and your account login email is under another name.