The Skype platform does not allow you to perform login which is always user initiated action (password).
SkypeKit API (C#) allows you to retrieve contact list from a running Skype application, after the user authorization. You can also use this API to initiate a call.
The SkypeKit API is deprecated and Microsoft is pulling the plug on it. I suggest you consider moving to some platform where you have guaranteed API availability.
https://stackoverflow.com/questions/17708758/alternatives-for-deprecated-net-skypekit