You update your login information via the app or the Idealist website!
To change your password or email address within the mobile app, first click on the three grey dots in the upper right hand corner of your profile and go to 'My account.' Here, you'll be able to update your email address, change your password, or disable your Idealist iOS account.
To change your password or email address from the Idealist website, log in to https://idealist.org, and access your profile to edit this information. You can see the exact steps here.
If you've forgotten your password, visit https://idealist.org, tap "Log In," then, "forgot password?" to start the password reset process.