If you choose the official route, the installation for Cinema 4D R23 is straightforward:
: The download contains files for multiple versions (R21, R23, R25, etc.). To ensure it loads correctly, delete all files except the one matching your version, such as c4dOctane-R23.xdl64 .
: OTOY offers a Free Tier of OctaneRender for personal use. This version is limited to a single GPU but includes most of the core features for learning and non-commercial projects.
: You won't be able to access the OTOY Forums for troubleshooting or new feature alphas.