From the Animation menu, select Animation Setup. Set the frame width and height to whatever size you want for the final render.

Arrange the scene.

Set your display mode to Cartoon+Line (CTRL-7).

From the Animation menu, select Make Movie (CTRL-J).

If you're rendering a single image (and not an animation), set the Sequence Type to Image Files, Resolution to Full, and Quality to Current Display Settings. Antialiasing is recommended. Adjust the time span to do a single frame only. Click OK.

Poser will ask for a filename and file type for the image, then starts rendering.

By the way, Cartoon+Line isn't a true cel shader. It only uses the material colour settings. No textures, bumps, reflections, or transparencies.