Download the .cam and .dru files from iteadstudio.com
Run the error check on the board. Tools:DRC, load the iteadstudio .dru file, click check.
If that comes back with only "stopmask" errors, you are ready to make Gerbers. If not, fix the errors.
Gerbers: File:CAM processor, File:Open:Job, select the iteadstudio .cam file, click Process Job.
You can download a free gerber file viewer from viewplot.com.
When ready, zip the 13 created files (but Not the .sch & .brd files) and send them to iteadstudio per their instructions after you make payment and have an Order #. Include the Order # with your files. I pay by paypal with them.