It sounds like you need to learn some of these mechanical basics before you're ready to start with Navigation. You need to use your wheel encoders and IMU to provide odometry for the robot base, usually over an /odom topic and TF with a odom->base_link transformation. Then hector slam or a localizer will provide the map->odom transform. Using robot_localization will help fuse your IMU and encoder information into a better state estimate (and the lidar odometry from Hector if you choose, or in place of the encoders).