VAR is just a zip file renamed. So make a copy of an existing VAR you've got, rename it to .zip, then extract it. Look at how they set it up. There is a JSON file that basically tells VAM everything that's in it. VAM loads your content from that. So replace the files, edit the JSON to point to your stuff. Once you're done, zip the file back up with Windows or Bandizip or whatever, then rename it to .var, instead of .zip.
Also follow the naming convention. Look at how VAR files are named: AuthorName.WhatsInTheVar.1.var where 1 is whatever version. VAM won't load it if it doesn't follow this.