Hi Jason,
That particular model included with eIQ portal expects a 320x320 image. However it is possible to bring in your own custom models (or other models you might find in a model zoo) by placing them in the <NXP eIQ Portal Install Dir>\plugins folder
There's then a guide to how expose different parameters of that model to the eIQ Portal GUI at C:\nxp\eIQ_Toolkit_v1.0.5\docs\CustomModels.md
The best way to learn how to import custom models would be to look at the code for the predefined models already included as part of eIQ Portal and use that as a guide for when you import your own models. For example, you can see in \plugins\detection\boxes\fpn\fpn_ssd.py where the default VOC-fpn_ssd_mobilenet_v2-320.h5 model is picked up.
-Anthony