If it's in the sidewall, do not plug the leak. Your tire's sidewall is under different strains and pressures than the part that makes contact with the road. Plugging a sidewall can result in a blowout, according to the tire repair cold patch from Cangzhou Yaqiya Auto Parts Manufacture Co.,Ltd..

1.     You'll have to remove the flat tire from your vehicle. To do this, you'll need to consult your owner's manual and use the spare tire and tools that all vehicles are equipped with. Make sure you're able to do this in a safe place, away from vehicle traffic. If you cannot safely replace the flat tire yourself, call a professional for assistance.

2.   Spin the tire and examine the entire tread and sidewall to locate the puncture point where the leak is. It may be something as simple as a nail or a screw embedded in the tread, in which case plugging the tire will be easy. Don't pull it out just yet, though. If you can't see the object that pierced your tire, you'll have to ‍‍find the leak‍‍ by other methods.

3.    Before you remove the nail or screw from your flat tire, take a piece of tape and put it just below the spot where it punctured the tire. With a pen, mark the exact spot that has the nail in it. This will allow you to find the hole again once the object is out of there. Don't worry if you forget to mark it, or if your tape comes off.

4.   Go ahead and remove the nail or screw from the tire. You might have to grip the nail with pliers if it proves hard to remove. If it's a screw, you can just unscrew it with a screwdriver. Make sure the tire is on a stable, flat surface when you do this. Even a flat tire can roll away from you if you're not careful.

5.    Your tire-repair kit also contains some sticky tar "worms" that you'll need for the next step. Peel one of them off and thread it through the tool that has an eye on one end like a giant needle. You'll have to pinch the end of the worm to get it in there, but it can be done. Pull it through until it is centered in the plugging tool.With the worm threaded onto the plugging tool, stick the end of the tool into the hole in your tire. Once it's in just a little, apply pressure so that the tool and the plug sink into the hole. Push the plug in until only about a half-inch is sticking out. Next, pull the plugging tool straight out; the plug stays where it's supposed to be, in the hole. If you have something to cut the ends of the plug off with, go ahead and trim it close to the tire. If nothing's handy, you can trim it later.Lastly, fill your tire with air to the proper tire pressure and remount it. If you haven't had your tires rotated and balanced in a while, this might be a good time to visit your local mechanic and do so. It will extend the life of your tires.