Follicle Ultrasound/Trigger Shot

Meghan • PCOS Warrior, blessed with a beautiful baby girl 4-18-17 via IUI and another beautiful baby girl 6-20-19 via IUI💕
Hello! Has anyone had a follicle ultrasound? If so, what can I expect? I go on Friday morning. 
After a follicle ultrasound, how soon do you do a trigger shot?