Asklemmy

Into lammps or in general? Because I havent really messed with LAMMPS so I wouldnt be able to reccommend resources for that yet. But if you mean in general, orca and gaussian are the easiest to use. Nwchem and gamess are a bit more obtuse with their documentation.

Chemcompute autogenerates input files and can be used to run simple calculations on a supercomputer but is limited to 1 hour with 1 core unless you are affiliated with their parner universities. In the latter case you can use up to 32 cores for longer periods of time. Currently it has support for gamess, tinker, jupyterhub, psi4 and namd: https://chemcompute.org/

ORCA has a wiki for input file documentation and use: https://sites.google.com/site/orcainputlibrary/visualization-and-printing

Avogadro, jmol and chemcraft are common drawing programs that can be used to draw molecules and visualize various properties. (ORCA uses .out as the extension of the output file, gaussian uses cube files and nwchem can be told to output data as cube files but again, is much more obtuse)

Avogadro manual: https://avogadro.cc/docs/

Jmol: https://wiki.jmol.org/index.php/Jmol_Tutorials

Nwchem: https://nwchemgit.github.io/Home.html

Gaussian: https://gaussian.com/man/

Gamess: https://www.msg.chem.iastate.edu/gamess/documentation.html