The export terrain window will pop up showing the mesh to be exported. The slider at the bottom can be moved to increase or decrease the polygons. Too much of an increase will lock the program. Try not to go above 10000
The exporter will also create texture maps. Diffusion ambient color, reflection, transparency, and bump components are available. The size refers to pixel size of the image textures. The format allows for bmp, jpg or other image types. To change each click on the down arrows and select from the menus. Once everything is selected click on the check button on the bottom right of the window. The mesh and images will be generated and the progress bar will appear. Then the window will close and leave you back in the terrain editor again.
Click the check button on the terrain editor to exit to the Bryce main window. Move the mouse to the top and click on the windows bar that appears. Click the word file and pull all the way down to the word quit. Save the Bryce file if you want then exit the program.