The documentation is built as follows.

1. Open a terminal
2. Install doxygen, on Ubuntu: $ sudo apt install doxygen
3. Change directory: $ cd /path/to/optas/doc
4. Run doxygen $ doxygen

If you want to read the documentation in a web browser then open html/index.html in Chrome/Firefox/etc.

If you want to read the documentation from a PDF, then you need to compile the documentation as follows.

1. $ cd /path/to/optas/doc/latex
2. $ make
3. Open the document refman.pdf