Alternatively, you can swap that image into another one you've captured to replace it.
The short answer to your question is that you eitther have to 1) capture an image in the console or 2) import an image via the resource import tool or you will NOT be able to use it via the console directly. In DS 6.9, you simply browsed to a folder, but in DS 7.5, because it is a part of the SMP, a "resource" must be created for a task to use it. Hense the resource import tool mentioned above. NOTE: If your image doesn't have the SMP agent in it, then any tasks AFTER you leave automation (generally post imaging) will fail because for those tasks to run, the agent must be installed and running after the image is rebooted. That's the only good way to import an image.
Unless you cheat.
Cheating is accomplished in several ways.
1) you can script the task fully instead of using the deploy image tasks. I don't generally recommend this for new users of the product or of imaging, but for those who are advanced, it can offer several advantages of control. A script task can be made to do just about anything, especially if you're adept at VBS. BUT, you have to own that process, adding more work up-front for you.
2) you can replace the image file of an image you DID capture in the console with the one you have sitting out on D. If you do this, in the right way (it's a bit weird, so if you don't know how, I'd say don't), then it "becomes" the image you had before. Works nice in very limited scenarios, but generally is NOT recommended.
Only the 1st method of cheating is generally recommended, and only for those who know what they're doing OR have a required custom method involving other things like manual driver replacement and/or manual injection of software including the altiris agent post imaging.
Sooooo, with that, for MOST people, using the resource import tool works.
NOTE: It will create a COPY of your image in a new location on the server, NOT use the image. It's important that you realize that when you use it. It creates a resource, and copies it to all the correct locations on the server and site servers. It does NOT utilizie the file you have on D. That becomes... well, sort of your personal backup. :D
GL!