SPICE, and in turn MaxQ require data about celestial bodies, the solar system, and Spacecraft so they can perform computations involving them.
The toolkits accept celestial data in the form of SPICE Kernel data files. These files come in a variety of underlying file formats and exist for a variety of purposes within the SPICE system.
Depending on what you’re attempting to do, you’ll need to know what kind of Kernel files you’ll need and where to get them.
For Aerospace industry professionals an extremely detailed SPICE Kernel reference is here: https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/C/req/kernel.html
Fortunately, using MaxQ in Unreal Engine for games and visualization purposes requires only basic knowledge of kernel data.