How to find the pose of a pattern

Hi, I am working on a project and i need to find the pose of a pattern but i don't know how to do it i know that some calibration package use it to calibrate the camera but i try to look inside but find nothings (i have miss something for sure but dunno what). Thanks you in advance ! Bwaki PS: i use Orbbec Astra camera already calibrate on Ubuntu 16.04 with ROS1 Kinetic