Computer simulations can be of great help in detailed studies of the adsorption of peptides on solid surfaces. Unfortunately, detailed simulations are limited to infinite dilution situations. Therefore, important characteristics of the adsorption phenomenon such as the morphology of adsorbed layer and the aggregation of the peptide at the solid surface remain unreachable. This prompted us to use the Extended Reference Interaction Site Model (XRISM) model for this purpose. A model 8-residues peptide (ASP-ASP-ILE-ILE-ASP-ASP-ILE-ILE) was used in this work. A model charged surface consisting of CH2 atoms with a fixed lattice arrangement was used. We studied the adsorption of this peptide at densities of practical interest. The first hydration layer for the peptide can be treated as the part of the structure of the peptide to include the solvation effects. To overcome the inability of the XRISM method to handle large number of interaction sites (which would arise by treating the peptide atoms explicitly) we used a Monte Carlo (MC) algorithm to find out the united residue potential of the peptide, where each amino acid is represented as a single site. A careful analysis of the correlation functions between the peptide and the surface allows us to determine the morphology of the adsorbed layer. Inspection of the pair correlation functions between adsorbed peptides shows the presence of clusters of different sizes.