Easy, leave the tin alone, in a cool and dark place. Visit as often as you like, but do NOT open the tin (until you are ready to ignite its contents). Easy.
For that we need the "mason jar". Or a whole bunch of them, depending on the quantity of tobacco you have. The Ball and Kerr brands are generally recognized as premium canning jars, so I would recommend these two names. Select jar size based on the volume of baccy you intend to store. The half pint jar holds about 2oz to 4oz of baccy, depending on its cut and consistency. Flakes, for example, are compressed, and with some tetris-dexterity one can cram quite a bit of the good leaf into a jar.
Select wide-mouth jars. They are just easier to scoop out from, and cost about the same as regular mouth jars. While I'm all for recycling and reusing, do NOT use a jar that has ever held any kind of foodstuff. Yes you can wash it, disinfect it, sterilize it, but just don't. Danged jars are dirt cheap, spring the nickel.
You can reuse jars that were used for baccy storage, sure. Just rinse with water, don't need no soap. But replace the lids, the rubber gasket gets squished after use and may fail in the future. Lids are dirt cheap, you cheapskate!
The best way to prepare jars is to simply run them through a dishwasher, just the jars (not lids, not bands, not your dinner plate either). Hot water, NO DETERGENT. Set the dishwasher to use the heated dry cycle. When the heater shuts off, you're ready. Do the filling quickly, you want the jars to be hot. Measure in your tobacco, leave like a quarter inch on the top for air space. Add lid, make sure no baccy is on the lip of the jar to compromise the seal area. Tighten band. As the jar cools, the air within also cools and contracts. The lid "nipple" will pop down (may take a day or a month, depending on how much air you left in there), ensuring a secured seal. And done! Easy! Don't forget the labels, with content and date clearly marked. Open after several years, enjoy.