Add the language labels for the new fields 

The language labels for the additional database fields should be added in Step 1 above. These will be used by the back end forms. The language labels used by the front end plugin should be added in the TS template setup using the method described in the Localization section of this document. For each language of interest to you with :phplanguageCode, which must be replaced by :phpde, :phpdefault or others. All cursive letters in the following examples must be replaced with your field names and texts. You may need the following statements for each additional field with myNewFieldName000: The basic field label:

Set the myNewFieldLabel into languageCode for myNewFieldName
plugin.tx_agency._LOCAL_LANG.languageCode.myNewFieldName = myNewFieldLabel
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The message displayed when the field is required but missing:

Set the missing_myNewFieldName for myNewFieldName
plugin.tx_agency._LOCAL_LANG.languageCode.missing_myNewFieldName = missingRequiredFieldMessage
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Same as previous but for the invitation form:

Set the missing_invitation_myNewFieldName for myNewFieldName
plugin.tx_agency._LOCAL_LANG.languageCode.missing_invitation_myNewFieldName = missingRequiredFieldMessageOnInvitationForm
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The following message displayed when a validation rule evalRuleName applicable to the field is not satisfied:

Set the evalErrors_evalRuleName_myNewFieldName for myNewFieldName
plugin.tx_agency._LOCAL_LANG.languageCode.evalErrors_evalRuleName_myNewFieldName = errorMessageForEvalRule
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Add fe_users.php 

TYPO3 reads in the $GLOBALS['TCA'] modified in your extension. Just add the new columns for your fields into the php:$GLOBALS['TCA'] of your file fe_users.php. This must be placed into the folder Configuration/TCA/Overrides of your extension.