You will need to log in to www.qatarairways.com and click under career. In there, all the departments are mentioned with the current available positions.

You will need to choose the available and interested position (all online) and click to "apply". There will be an online application form and it differs from position to position and to department to department.

There will be a application number or a code appears once you apply for that position. Keep that with you for further reference or future checking. They will most probably contact you via email and phone. If not check again or re-send the application.

Good Luck!