Resolution Problem

[Art999]

I'm getting into HDR. I have Photomatrix and Topaz Adjust. After taking the photo (RAW) through the various programs, I come out with a resolution of 240. As I usually print at a minimum of 16x20, I would like to finish at at least 300 dpi, but have been unable to figure out how to do this. I posted this in a different area a few weeks ago: had about 150 viewers, but not one single answer. I would appreciate an answer, even if it's just to tell me where I could try next. Thank you.

Art999