If you forgot your password, just visit https://app.involve.me and click on "Forgot password?" below the Login button. Then enter your E-Mail address and you will get a reset-link sent to your address.
To set a new password when logged in, navigate to the dropdown under your User Name and select "Account Settings".
In the Change Password screen, you'll be able to set up a new password for your account by entering the old one and confirming the new one.