It will be very helpful if you can try to establish a routine for changing your pouch. A good rule of thumb, when using a closed pouch, is to change your pouch every time your ostomy has worked.
Output from a colostomy is not too different from normal bowel movement. The output is generally solid, and the pouch needs changing between one and three times a day.

Is changing the pouch difficult?
The first few times, it will almost certainly feel challenging. Make sure that the first couple of times you try changing the pouch, you do it somewhere you feel safe and comfortable.
Take your time– it is completely okay if at first you don’t get it right every time. Though it may take some getting used to, it will soon feel like a routine matter to you.
Before use, always consult the 'Instructions for use' document delivered with the products