Q: How can I make a call from iPad

You can do FaceTime calls over wifi and calls via, for example, Skype with their iPad app, but you can't make 'normal' phone calls from an iPad.

Use of of the many VOIP apps from the App Store.  Note that the iPad cannot make a cellular call.

Oh, you have to get the iPhone app.

Seriously, though .... you are aware that it's not a telephone, right? Any calls you make will be using VOIP and any of the apps and/or services (Skype, Google Talk, etc., etc.) which support that. Some of those are US-only, all have various restrictions and cost structures.