The first few times you change your colostomy pouch it will likely feel challenging. Make sure that the first few times you change your pouching system, you find a location in which you feel comfortable.
Take your time - it is fine if at first you don't get it right every time. Soon, it will become a routing and more familiar to you.

Getting into a routine
It may be helpful for you to establish a routine for changing your pouch. Changing your pouch at a time when your ostomy is realtively inactive, like first thing in the morning, may be a good plan to establishing a routine.

How often does your pouching system need to be changed?
The frequency of pouching system changes depends on many things, however, you would want to change your pouching system if you feel itching or burning of the skin around your stoma.
Output from a colostomy is not too different from a normal bowel movement. The output is generally solid, and the pouching system needs changing typically one to three times a day.
Before use, always consult the 'Instructions for use' document provided with the product