When you chose a print and are ready to send it to the mill for printing you need to 1. confirm the scale or size of the print 2. make sure the print is in repeat. A typical print is done in a 25" screen repeat. Large prints can jump to 36" screen repeat size 3. Pitch your print into your desired colors... remember each color is it's own screen (and number of screens will add to your cost). Typically a print will be no more than 10 to 12 colors total for mass market.
See attached image for an example of a pitch sheet.