I followed the pages in the web: http://turtlebot3.robotis.com/ from the web i entered the PCsetup from Quick Start Guide and i run all the code in that page then from the simulation i run all the code in Gazebo Simulation and SLAM Simulation i faced a problem, when i tried to Launch Simulation World the simulation window closed for no reason so i solved this problem by using this code:
then i retry to open the simulation and finally it opened correctly last thing is that i complete the map by moving the robot using the following keystrokes w s a d and then i save the map, that's it.