Popsie, I used to help children with spina bifida learn this technique. It's helpful to use a mirror when you're starting out. A magnifying makeup mirror with a stand usually works the best, although the magnification throws some people off and they choose to use the non-magnified reverse of the mirror. I'm sure your doc will send you to a nurse or therapist who will help you with the process.
The idea is not to let your bladder fill and back urine up into your kidneys, as the pressure this causes can damage the kidneys. Also, urine standing in the bladder for a long time predisposes you to chronic bladder infections which can also move into the kidneys.
Hopefully the meds will work and you won't need to catheterize. There is also an old technique called crede (cre-day) which involves external pressure on the bladder to help empty it more completely. You might ask your doctor about that. Good luck!