Your doctor will advise you when to use your nitroglycerin tablets

Sit or lie down to take your nitroglycerin. If you are driving, pull over and park the car. Taking nitroglycerin can lower your blood pressure, which could cause you to pass out if you are standing up.

Place the under-the-tongue (sublingual) tablet under your tongue. Leave it there until it dissolves. If you accidentally swallow the tablet, take another. The medicine won't work if it is swallowed.
Place the between-cheek-and-gum (buccal) tablet between your cheek and gum. Leave it there until it dissolves. If you accidentally swallow the tablet, take another. The medicine won't work if it is swallowed.

Take one tablet as directed by your doctor.  Ask him what to do if you do not get relief within a very short time. He may tell you to take another tablet after 3 to 5 minutes. 

Ask your doctor to tell you when you need to call 911 or other emergency services.  If the pill doesn't work you are in an extreme emergency situation.

Your tablets will come to you in a brown glass bottle.  Commonly they are available in 100 tablet bottles or a set of 4 very small bottles, each holding 25 tablets.  Warmth, moisture and light will damage the tablets.

Do not carry the bottle of tablets in your pants pocket.  Your body warmth will hurt them.  It is safe to carry them in a jacket or purse.

There is no cotton filler in the bottle as you will usually find in any other pill bottle.  That is because the nitroglycerin tablets are unstable and will lose their potency if they come in contact with any other substance other than glass.  Therefore, do not take the tablets out of the glass bottle to put them in a plastic or metal pill holder.  That will ruin them. 

Here are pictures of products we have seen advertised specifically as nitroglycerin tablet holders.  Don't use them.  They will degrade your tablets if you use them.  You need to keep the tablets safe.