Go here, scroll down, and click Download.
Download & unzip the files for Eagle.
Put the .dru file in the eagle /DRU folder, and .cam in the /CAM folder.
(.drc file? I don't remember)
When your design is created, and you're satisfied with the error rule check (ERC) on the schematic,
and you're happy with the board design,
use the .dru file for the design rule checks on the .brd file. Fix any errors.
There are usually a bunch of Stop Mask errors, especially if you have any headers. I usually ignore them if I am satisfied with the markings presented.
(You can right-click & SMASH components, then move names around, resize them, etc. If you get too confused, Unsmash & start over with a fresh Smash. Really helpful if you delete a name by accident)
When satisfied, create the gerbers. From the .brd file, its a 2-step process.
(this reads more complex than it is)
File:CAM processor, new message box opens
File:Open:Job:select the itead .cam file
then click Process Job. Bunch of files get created, 13 total.
You can download a free viewer from viewplot.com to check them out.
When satisfied, put the 13 created files (but not your .sch and .brd files) in a zip file, that's you send to itead.
Order PCBs, you'll get a Order # back.
Send the Order # and your zip file to email@example.com
(this is all from memory, but its pretty close)