I do not have my printer set up at the moment, but this SHOULD be pretty straight forward.  For the main body, just print it out at 100% scale.   It should hold the normal 2"x3.5" cards just fine.

For the logo, just take the small round piece into tinkercad or your program of choice, and import an SVG of your logo and place it over the round piece.  Group it, save it, and print it.  

I only planed for this to have one logo for my purposes, but if you have multiple logos that you need to change out, you can possibly drill out the back and add some flat magnets, and do the same for the main body.  That SHOULD work if you don't drill too far