As an administrator of your organization you have access to your member's profiles on the People tab. While the standard MemberHub profile information is necessary you may need to track, record and maintain other information about your members. This is what Custom Fields are for.
To create custom fields, access your Admin Console, click on the Settings tab and then click on the Custom Fields link in the sidebar navigation.
Click the Add Field button and you can choose from various field types (Text, Multiline, Numeric, Dropdown, Checkbox and Date)
After you create you custom fields you can edit the value of those fields for each person in your organizaiton. Access the People tab and simply click on a person's name. You'll then a notice a new section under the person's regular member data. Click the Edit button and you'll be able save custom information for that person record. While you edit the profile, custom fields are listed last among profile information
If you mark the custom field as "Editable by the member on their profile" then members will have the ability to edit the data for that field about themselves on their profile. Upon creating their account and joining your organization, people will be prompted to complete their profile.