Hi sodizavc and welcome to Voipuser
You are making things more complicated by asking two questions in one

and not telling us clearly what you want to achieve. Adding the settings for Voipdiscount or for any other service is just a question of substituting username, password, and server address for that service.
Is it the case that you haven't made it work with or managed to log into any provider? If so then just post the settings you have problems with and we can take a look. Perhaps its just a question of setting up the dial plan so all calls go out via Voipdiscount ? If its that then please just let us know. We need a bit more info from you really on exactly what you have done so far and which bits work and which don't - to be able to help properly.