Lowes sold me two 00 when I bought my wire to install a 100 amp sub panel for my shop. only 3 wire that feed into my outside disconnect. What will be the correct way to instal the 4 wire?
How far is the sub panel from the main panel? Did they sell you Al or CU? 2/0 is awful big for a 100amp sub panel.
The feeder must be protected with a breaker of its own. What size breaker is feeding the sub panel?
Is the garage attached or un-attached?
You have many questions to answer before we can do anything to help you.