This directory has two input scripts that illustrates how to use fix charge_regulation in LAMMPS to perform coarse-grained molecular dynamics (MD) simulations with incorporation of charge regulation effects. The charge regulation is implemented via Monte Carlo (MC) sampling following the reaction ensemble MC approach, producing a MC/MD hybrid tool for modeling charge regulation in solvated systems. The script `in.chreg-acid` sets up a simple weak acid electrolyte (pH=7,pKa=6,pI=3). Four different types of MC moves are implemented: acid protonation & de-protonation, and monovalent ion pair insertion and deletion. Note here we have grouped all free monovalent ions into a single type, a physically natural choice on the level of coarse-grained primitive electrolyte models, which increases the calculation performance but has no effects on thermodynamic observables. The variables such as pH, pKa, pI, and lb at the top of the input script can be adjusted to play with various simulation parameters. The cumulative MC attempted moves and cumulative number of accepted moves, as well as, current number of neutral and charged acid particles, neutral and charged base particles (in this example always 0), and the current number of free cations and anions in the system are printed in the output. The script `in.chreg-polymer` sets up a weak poly-electrolyte chain of N=80 beads. Each bead is a weak acid with pKa=5 and solution has pH=7 and monovalent salt chemical potential pI=3. In this example, we choose to treat salt ions, protons, and hydroxyl ions separately, which results in 5 types of MC moves: acid [type 1] protonation & de-protonation (with protons [type 4] insertion & deletion), acid [type 1] protonation & de-protonation (with salt cation [type 2] insertion & deletion), water self-ionization (insertion and deletion of proton [type4] and hydroxyl ion [type 5] pair), insertion and deletion of monovalent salt pair [type 2 and type 3] , insertion and deletion of a proton [type4] and salt anion [type 3]. The current number of neutral and charged acid particles, the current number of free salt cations and anions, and the current number of protons and hydroxyl ions are printed in the output.