TNL currently lacks well written documentation. We are, however, working hard on it.
User Guide Developer Guide
This tutorial will explain how to work with vectors ...
Tutorial: Vector operations
Fučík R., Klinkovský J., Solovský J., Oberhuber T., Mikyška J., Multidimensional Mixed–Hybrid Finite Element Method for Compositional Two–Phase Flow in Heterogeneous Porous Media and its Parallel Implementation on GPU, Computer Physics Communications, accepted dec 2018, doi.org/10.1016/j.cpc.2018.12.004.