Running an MD simulation with LAMMPS is simpler. In the LAMMPS input file, one needs to specify the pair style as follows
pair_style deepmd graph.pb
pair_coeff * * O H
where graph.pb is the file name of the frozen model. pair_coeff maps atom names (O H) with LAMMPS atom types (integers from 1 to Ntypes, i.e. 1 2).