how definition geometry_msgs/Pose for link ??

edit

hi . i want to plot position x of /my_robot/pose topic, which is a type of geometry_msgs/Pose message. This can be plotted by /your_robot/pose/position/x. in this page say :

step one -- >> geometry_msgs/Pose contains a member position. Look into its definition by clicking the link at geometry_msgs/Point in the api page. step two -->> You see x as a member of geometry_msgs/Point.

how can i doing step one ?? where is a api page ?? how can i write geometry_msgs/Poin for links ?? i want ploot pose of link in rqt like this : /your_robot/pose/position/x