Call Apex Action

var actionName = component.get("c.methodName");
actionName.setParams({
  "paramName" : value
});
actionName.setCallback(this, function(response) {
  var state = response.getState();
  if (state === "SUCCESS") {
    var returnValueVar = response.getReturnValue();
  }
  else if (state === "ERROR") {
    var errors = response.getError();
  }
});
\$A.enqueueAction(actionName);