I am new to winbox and I have a hotspot setup but when my wireless clients pay and then attempt to log in they are not able to authenticate with the external radius servers.
I figured by configuring radius that this would allow any internal/external radius request to work. I am using NTradPing and it still fails internally, could someone tell me how to add two nat entries which would allow any wireless client to communicate to external radius servers?

Do you have radius logging enabled? Try a login and check the log. That may help you figure out what is happening. If the radius server does not respond, insure you have that hotspot router entered as a client in the radius settings in the server.