Everything that can be done with Obi in Unity's editor can also be done at runtime. In addition to this you can also query the simulation, detect contacts, create blueprints and actors, etc.
In order to use Obi in your own scripts, you need to include the Obi namespace at the top:
using Obi;
If you're using assemblies in your project, you will also need to reference Obi's assembly from your assembly definition files. Once this is done you're ready to start writing code.