Usually through the internal network or promotions. When there is a specific need for an industry or technical expertise, they post a job position for this. Go through a HR screening process first followed by 2-3 rounds of interviews.
Interview questions [1]
Question 1
what's the most difficult project you managed and how to overcome? Here, you must be very detailed oriented to explain your strength as well as weakness and how you are going to do well at IBM in the future based on this experience