The method includes a first step of providing a housing with a hollow protrusion. A second step provides an auxiliary element in the hollow protrusion. A third step provides a connector receptacle in connection with the auxiliary element. A fourth step inserts a matching connector in the connector receptacle in a detachable way, the matching connector further including guiding means. A fifth step places a luminous module including a module connector, the module connector being helped by the guiding means to be connected to the matching connector, to achieve an electric connection between the module connector and the matching connector. A final step moves the connector receptacle so that the matching connector exits from the connector receptacle.