Pour out 1/3 of the bottle of vinegar and reserve for another use.
Fill that space in the vinegar bottle with extra virgin olive oil.
Remove any plastic pouring top that might be on your vinegar in order to get the garlic in the bottle. Or if you have trouble taking that top off you may have to chop your garlic into smaller bits to go in the top.
Add the garlic pepper to the bottle as well.
Let the dressing sit for a couple of days to let the seasonings blend together. I store mine in the cabinet because none of the ingredients require refrigeration.
Shake well before using.