Visit any local hardware store that is nearest from your place, and purchase a sealer that is especially made for sealing granite counter tops. If you cannot find one in your nearest hardware store, try finding it at a better hardware store. There would be plenty of granite counter top sealers available. You should purchase one that is not very expensive, and will do the job effectively.
After you have purchased the sealer, return to your place. Remove all the items placed over the granite counter top, and set them aside at a safe place. Take a soft but clean rag, and start wiping off any crumbs or dust from the surface of the granite counter top.
Now take the counter top stone cleaner, and start cleaning your granite counter top. Spray it all over the top, and let it sit for around 30 seconds to 45 seconds. Take a clean sponge, and start cleaning your counter top. Dry the whole top with a clean but dry towel.
With the help of a clean cloth or a tooth brush, start applying the sealer to the granite counter top. Allow the applied sealer to sit for around 3 to 4 minutes at least. Apply another coat of the seal once your first coat has completely dried up. Once your second coat of the sealer has also dried up, start rubbing the sealer into the granite counter top with the help of a clean cloth.
Allow all the sealer to dry up. It will not take more than 30 minutes to completely dry up. However, there are some sealers that could take up to 2 to 3 hours. Repeat all the process of applying the sealer once again, as it will perfectly seal up your granite counter top.