The calculation of one-loop Wilson coefficients for general Beyond the Standard Model (BSM) scenarios is a technical challenge often addressed by doing long and error prone analytical calculations by hand. Several software programs already provide squared amplitude calculations at the loop-level, but few of them are also able to derive general loop-level Wilson coefficients necessary e.g. for the study of quark decays in flavor physics. MARTY, a computer program that automates tree-level and one-loop perturbative calculations for general BSM scenarios can in particular be used to obtain such Wilson coefficients. We present in details the simple user interface allowing to derive common Wilson coefficients in MARTY, and the most general use case of MARTY to extract the coefficient of any effective operator.