Select Program➔ Set Reference Frame Instruction to use a specific reference frame. This will update the given reference frame on the controller for the following movement instructions and will change the Active reference frame of the robot in RoboDK for simulation purposes. That means that movement instructions to specific targets (Cartesian targets) will be made with respect to the last reference frame set.
The reference frame is a variable also known as Work Object (ABB robots), UFRAME (Fanuc robots), FRAME (for Motoman robots) or $BASE (for KUKA robots).