When signed into your Platform account, you are able to change the email address, password, language, default URL for new TouchPoints and a few other things in the Account Overview and Preferences sections. Tap the avatar icon in the upper right corner and select one of the settings you'd like to change and update the desired fields.
If you're a subscriber to the higher tiers of the platform, there are more features available like adding more users to your account setting their individual access. Take a look below at how the enterprise tier of the platform looks when adding new users.
Once the new user accepts the invite, you as the account owner, are able to set their level of access on your account.