You would add the color change and probably set a choke and spread if you're using more than one spot color. Depending on the colors used, you may also choose to just set CMYK colors instead of spot colors .... especially if you have a CMYK image already being run. This nearly always eliminates the need for chokes and spreads. If you want to reduce or eliminate any graininess in these fills, select a halftone type of Classical Dot and bump the LPI setting up into the 70 to 90 range.
To run it with the entire image behind it showing, you set the text to overprint and turn all cuts off. then set a rectangle or whatever shape you want to use to cut out the image.
Learning the different ways to achieve any given effect is different with Omega and in general when you are working with spot colors. Your tools are:
Cuts On or Off
Spot or CMYK
Overprint or Not (Not knocksout all print beneath it)
Clear Fills
Printing on films other than white .... with or without primers.
Hope this helps.