To define parameters you declare the type, then the parameters itself so on your method you have the type but are missing the parameter name. Fix it by adding changing it to something like this:
public void Myf(Form myVariable)
then in the method, you already have an instance of the type you declared, so you don't need to create a new instance
public void Myf(Form myVariable)
{
myVariable.... // do stuff with it
}
And the problem with the second section is that you;re trying to pass the type through, when it requires an instance of the type. And in your case your instance is the Form you ar currently in, so to pass that into it you use this
, ie
Myform mf = new Myform();
mf.Myf(this);
Although the way you seem to be trying to do things doesn't seem right, and I think will cause a lot of problems for you in the future. If you can explain exactly what you;re trying to do maybe we can suggest a better way to do it?
Hope that makes some sense!