There is currently no documentation for xcanvas, though you can look at the ipycanvas documentation as xcanvas aims at providing the same API. You can also find an example notebook on the repo.
Note that xcanvas does not (yet) provide the full implemtation that ipycanvas provides.
conda install xeus-cling xcanvas -c conda-forge
First install dependencies (here using conda):
conda install cmake xwidgets xeus xeus-cling ipycanvas -c conda-forge
Then compile:
mkdir build
cd build
cmake -D CMAKE_INSTALL_PREFIX=$CONDA_PREFIX ..
make install