A new method of numerical simulation of the magnetization of layered high-temperature superconductors (HTSCs) with arbitrary pinning centres has been developed. A HTSC plate with a finite width in the x-direction and an infinite width in the y-direction was considered in a perpendicular external magnetic field. We have minimized a free energy functional by means of the Monte Carlo technique. This procedure allowed us to obtain an equilibrium number of vortices and vortex configurations inside the plate at the various external magnetic fields and so to calculate magnetic induction B(H,T) and magnetization M(H,T). Magnetization curves have been obtained for a cyclical change of the external magnetic field at different temperatures and defective states of the superconductor. The crossover from surface to bulk pinning was demonstrated. The magnetic flux profiles inside a superconductor were calculated. It was shown that the Bean model is true for strong pinning only.