First of all it would help if you could give us the Name of the TA.
In most TAs is an README File qhere you can find further Instructions.
For the credential Setup.
Take a look in your "%splunkroot%\etc\apps[TA_NAME]\default" directory.
Are there some config files? If yes, take a look at them. (please DONT edit them)
If you can find the nessesary parameters, copy the Files you need to edit to "%splunkroot%\etc\apps[TA_NAME]\local" and edit them there.