Run cargo build - it will download the prebuilt artifacts from bochscpu-build and extract the lib and bochs folders into the bochscpu checkout.
This will result in a tree like follow:
bochscpu$ ls -l
total 20
drwxrwxrwx 1 x x 4096 Jan 3 00:09 bochs # bochs directory from pre-built artifacts
-rwxrwxrwx 1 x x 8318 Jan 2 23:28 build.rs
drwxrwxrwx 1 x x 4096 Jan 2 23:28 cabi
-rwxrwxrwx 1 x x 4772 Jan 3 00:16 Cargo.lock
-rwxrwxrwx 1 x x 427 Jan 2 23:28 Cargo.toml
drwxrwxrwx 1 x x 4096 Jan 3 00:09 lib # lib directory from pre-built artifacts
-rwxrwxrwx 1 x x 502 Jan 2 23:28 README.md
drwxrwxrwx 1 x x 4096 Jan 3 00:20 src
drwxrwxrwx 1 x x 4096 Jan 3 00:16 target
-rwxrwxrwx 1 x x 276 Jan 2 23:28 TODO.md
bochscpu exposes all the instrumentation points that bochs does. These are documented here.
For an example of initalizing and using the emulator, see the source code for the benchmark example.