Homocysteine covalently bonded with a protein MD simulation how to perform

GROMACS version: 2021
GROMACS modification: Yes/No
How do I perform MD simulation of protein covalently bonded with homocysteine, how do I do the parametrization, it seems very complex can someone help and tell me in detail? The homocysteine is covalently bonded with disulphide bond with cysteine residue