First, you need to compile to get the shared library:
# Debug build
cargo build
# Release build
cargo build --release
The .so will be in the target/debug or in the target/release
directory, depending on how you built it. You can then use it to
dynamically link with a C project, load it dynamically at runtime with
dlopen
(and things that use it under the hood, like Python's
ctypes library), etc...
You can also generate the C header with cbindgen:
cbindgen -o scryer_prolog.h
All the API functions are documented in the source and in the generated header.
There are also examples of usage from C in the c_examples directory.