In ovarian stimulation, the patient injects medication for approximately 2 weeks in order to mature several follicles within the ovaries at the same. To prevent premature ovulation, another medication must also be added. As soon as the follicles are large enough, ovulation is specifically induced and the eggs are then collected using an ultrasound guided needle aspiration via the vagina. The eggs are usually frozen unfertilized and are available for later medical assisted reproduction.
An english version can be bought: Fertility Preservation in Oncological and Non-Oncological Diseases a practical guide by Michael von Wolff & Frank Nawroth ISBN 978–3‑030–47567‑3 from Springer.com
Part III.I page 169ff.