Don't take this information without solid proof, but last time, before there were Head Wizards appointed, people made a staff app as normal and included pictures of builds they have done on the server.
This was until there was a Head Wizard appointed.
No you do not fill out an application on the forums. It is different, first you have to build your own build on Mianite in Survival and show me when you're done. If you pass that stage then you need to go to /Server Creative and build a build in creative then show me when you're done if you pass both those tests you will probably get Wizard.