Fast-steering Secondary Mirror prototype (FSMP) of the Giant Magellan Telescope (GMT) has been developed by the consortium consisting of institutes in Korea and the US. In 2014 we are finalizing the FSMP project as combining two sub-systems, the mirror fabricated by Korea Research Institute of Standards and Science (KRISS) and the mirror cell with tip-tilt controlling system developed by Institute for Advanced Engineering (IAE), in the KRISS facility. In the assembly process we will identify potential difficulties or problems for the process, such that this process can be reflected to the further development of the FSM for GMT. In the presentation, we present how the assembly process can be carried out in safety.