Find the spare wheel, jack and wheel wrench which may be under the boot floor, under the car or on the back door. You'll get dirty hands and knees so consider carrying gloves and a newspaper to keep clean.
If you can't find a spare wheel your car may be equipped with inflating mousse which can be squirted into the tyre via the valve. This is only a get-me-home solution, though. Get the tyre changed as soon as possible.