Here are a few tutorials to get started using LAMMPS. I have also modified a number of these tutorials and updated with Python routines within Jupyter Notebooks, see my GitHub LAMMPS tutorial website.
The input decks and the tutorial for beginners to LAMMPS can be viewed online in the LAMMPS Beginner Help.
A video tutorial and demonstration for running LAMMPS can be found here.
A short introduction and tutorial for LAMMPS can be found in these videos: